Publications

@article{RN100,

title = {Thermo-mechanical characterization of metal/polymer composite filaments and printing parameter study for fused deposition modeling in the 3D printing process},

author = {Seyeon Hwang and Edgar I Reyes and Kyoung-sik Moon and Raymond C Rumpf and Nam Soo Kim},

url = {https://link.springer.com/content/pdf/10.1007%2Fs11664-014-3425-6.pdf},

doi = {DOI: 10.1007/s11664-014-3425-6},

issn = {1543-186X},

year  = {2014},

date = {2014-10-29},

journal = {Journal of Electronic Materials},

volume = {44},

number = {3},

pages = {771-777},

abstract = {New metal/polymer composite filaments for fused deposition modeling (FDM) 

processes were developed in order to observe the thermo-mechanical properties of the new filaments. The acrylonitrile butadiene styrene (ABS) thermoplastic was mixed with copper and iron particles. The percent loading of the 

metal powder was varied to confirm the effects of metal particles on the 

thermo-mechanical properties of the filament, such as tensile strength and 

thermal conductivity. The printing parameters such as temperature and fill 

density were also varied to see the effects of the parameters on the tensile 

strength of the final product which was made with the FDM process. As a 

result of this study, it was confirmed that the tensile strength of the composites is decreased by increasing the loading of metal particles. Additionally, 

the thermal conductivity of the metal/polymer composite filament was improved by increasing the metal content. It is believed that the metal/polymer 

filament could be used to print metal and large-scale 3-dimensional (3D) 

structures without any distortion by the thermal expansion of thermoplastics. 

The material could also be used in 3D printed circuits and electromagnetic 

structures for shielding and other applications.},

keywords = {3D printing, copper, fused deposition modeling, iron, large-scale 3D  printing, Metal/polymer composite filament, thermo-mechanical properties},

pubstate = {published},

tppubtype = {article}

}

@article{RN95,

title = {Concept and model of a metamaterial-based passive wireless temperature sensor for harsh environment applications},

author = {Hasanul Kairm and Diego Delfin and Mohammad Arif Ishtiaque Shuvo and Luis A Chavez and Cesar R Garcia and Jay H Barton and Sara M Gaytan and Monica A Cadena and Raymond C Rumpf and Ryan B Wicker},

url = {https://ieeexplore.ieee.org/document/6924738?arnumber=6924738},

doi = {10.1109/JSEN.2014.2363095},

issn = {1530-437X},

year  = {2014},

date = {2014-10-15},

journal = {IEEE Sensors Journal},

volume = {15},

number = {3},

pages = {1445-1452},

abstract = {Wireless passive temperature sensors are receiving increasing attention due to the ever-growing need of improving energy efficient and precise monitoring of temperature in high-temperature energy conversion systems, such as gas turbines and coal-based power plants. Unfortunately, the harsh environment, such as high temperature and corrosive atmosphere present in these systems, has significantly limited the reliability and increased the costs of current solutions. Therefore, this paper presents the concept and design of a low cost, passive, and wireless temperature sensor that can withstand high temperature and harsh environments. The temperature sensor was designed following the principle of metamaterials by utilizing closed ring resonators in a dielectric ceramic matrix. The proposed wireless, passive temperature sensor behaves like an L C  circuit, which has a temperature-dependent resonance frequency. Full-wave electromagnetic solver Ansys Ansoft HFSS was used to validate the model and evaluate the effect of different geometry and combination of split ring resonator structures on the sensitivity and electrical sizes of the proposed sensor. The results demonstrate the feasibility of the sensor and provide guidance for future fabrication and testing.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{RN92,

title = {Finite-difference frequency-domain algorithm for modeling electromagnetic scattering from general anisotropic objects},

author = {Raymond C Rumpf and Cesar R Garcia and Eric A Berry and Jay H Barton},

url = {https://www.jpier.org/pierb/pier.php?paper=14071606},

doi = {doi:10.2528/PIERB14071606},

issn = {1937-6472},

year  = {2014},

date = {2014-09-12},

journal = {Progress In Electromagnetics Research B},

volume = {61},

pages = {55-67},

abstract = {The finite-difference frequency-domain (FDFD) method is a very simple and powerful approach for rigorous analysis of electromagnetic structures. It may be the simplest of all methods to implement and is excellent for field visualization and for developing new ways to model devices. This paper describes a simple method for incorporating anisotropic materials with arbitrary tensors for both permittivity and permeability into the FDFD method. The algorithm is benchmarked by comparing transmission and reflection results for an anisotropic guided-mode resonant filter simulated in HFSS and FDFD. The anisotropic FDFD method is then applied to a lens and cloak designed by transformation optics.},

keywords = {finite-difference frequency-domain (FDFD), finite-difference frequency-domain (FDFD)},

pubstate = {published},

tppubtype = {article}

}

@article{RN80,

title = {All-dielectric frequency selective surface for high power microwaves},

author = {Jay H Barton and Cesar R Garcia and EA Berry and RG May and DT Gray and RC Rumpf},

url = {https://ieeexplore.ieee.org/document/6807717},

doi = {10.1109/TAP.2014.2320525},

issn = {0018-926X},

year  = {2014},

date = {2014-04-29},

urldate = {2014-04-29},

journal = {IEEE Transactions on Antennas and Propagation},

volume = {62},

number = {7},

pages = {3652-3656},

abstract = {In this work, an all-dielectric frequency selective surface was developed for high power microwaves. By avoiding the use of metals, arcing at field concentration points and heating in the conductors was avoided. To do this in a compact form factor while still producing a strong frequency response, we based our design on guided-mode resonance (GMR). To make this approach viable for radio and microwave frequencies, we overcame three major challenges. First, conventional GMR devices have less than 1% fractional bandwidth and we extended this to 16%. Second, conventional GMR devices have a field-of-view less than 1 °  and we extended this to over 40 °  . Third, conventional GMR devices must be composed of hundreds of periods to operate, but our device operated very well with only eight. In this paper, we present our design and experimental results at 1.7 GW/m 2  .},

keywords = {guided mode, resonance},

pubstate = {published},

tppubtype = {article}

}

@article{RN122,

title = {Metamaterial based passive wireless temperature sensor},

author = {Hasanul Karim and Diego Delfin and Luis A Chavez and Luis Delfin and Ricardo Martinez and Jose Avila and Carlos Rodriguez and Raymond C Rumpf and Norman Love and Yirong Lin},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adem.201600741},

issn = {1438-1656},

year  = {2014},

date = {2014-02-14},

journal = {Advanced Engineering Materials},

volume = {19},

number = {5},

pages = {1600741},

abstract = {This paper presents the fabrication, modeling, and testing of a metamaterial based passive wireless temperature sensor consisting of an array of closed ring resonators (CRRs) embedded in a dielectric material matrix. A mixture of 70 vol% Boron Nitride (BN) and 30 vol% Barium Titanate (BTO) is used as the dielectric matrix and copper washers are used as CRRs. Conventional powder compression is used for the sensor fabrication. The feasibility of wireless temperature sensing is demonstrated up to 200 °C. The resonance frequency of the sensor decreases from 11.93 GHz at room temperature to 11.85 GHz at 200 °C, providing a sensitivity of 0.462 MHz °C. The repeatability of temperature sensing tests is carried out to quantify the repeatability. The highest standard deviation observed is 0.012 GHz at 200 °C.},

keywords = {closed ring resonators, metamaterials, passive wireless temperature sensor, sensors},

pubstate = {published},

tppubtype = {article}

}

@article{RN93,

title = {Tight control of light beams in photonic crystals with spatially-variant lattice orientation},

author = {Jennefir L Digaum and Javier J Pazos and Jeffrey Chiles and Jeffrey D’Archangel and Gabriel Padilla and Adrian Tatulian and Raymond C Rumpf and Sasan Fathpour and Glenn D Boreman and Stephen M Kuebler},

url = {https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-22-21-25788&id=303042},

doi = {https://doi.org/10.1364/OE.22.025788},

issn = {1094-4087},

year  = {2014},

date = {2014-02-01},

journal = {Optics express},

volume = {22},

number = {21},

pages = {25788-25804},

abstract = {Spatially-variant photonic crystals (SVPCs), in which the orientation of the unit cell changes as a function of position, are shown to be capable of abruptly controlling light beams using just low index materials and can be made to have high polarization selectivity. Multi-photon direct laser writing in the photo-polymer SU-8 was used to fabricate three-dimensional SVPCs that direct the flow of light around a 90 degree bend. The lattice spacing and fill factor were maintained nearly constant throughout the structure. The SVPCs were characterized at a wavelength of 2.94 μm by scanning the faces with optical fibers and the results were compared to electromagnetic simulations. The lattices were shown to direct infrared light of one polarization through sharp bends while the other polarization propagated straight through the SVPC. This work introduces a new scheme for controlling light that should be useful for integrated photonics.},

keywords = {low index materials, spatially variant photonic crystals},

pubstate = {published},

tppubtype = {article}

}

@article{RN79,

title = {Electromagnetic isolation of a microstrip by embedding in a spatially variant anisotropic metamaterial},

author = {Raymond C Rumpf and Cesar R Garcia and Harvey H Tsang and Julio E Padilla and Michael D Irwin},

url = {https://www.jpier.org/PIER/pier.php?paper=13070308},

issn = {1070-4698},

year  = {2013},

date = {2013-09-02},

journal = {Progress In Electromagnetics Research},

volume = {142},

pages = {243-260},

abstract = {The near-field surrounding devices can be arbitrarily sculpted if they are placed inside a spatially variant anisotropic metamaterial (SVAM). Our SVAMs are low loss because they do not contain metals and are extraordinarily broadband, working from DC up to a cutoff. In the present work, a microstrip transmission line was isolated from a metal object placed in close proximity by embedding it in an SVAM so that the field avoided the object. Our paper begins by outlining a simple finite-difference modeling approach for studying transmission lines embedded in SVAMs. We then present our design and experimental results to confirm the concept.},

keywords = {spatially variant anisotrpoic metamaterial (SVAM), spatially variant anisotrpoic metamaterial (SVAM)},

pubstate = {published},

tppubtype = {article}

}

@article{RN85,

title = {Broadband microwave frequency characterization of 3-D printed materials},

author = {Paul I Deffenbaugh and Raymond C Rumpf and Kenneth H Church},

url = {https://ieeexplore.ieee.org/document/6574280},

doi = {10.1109/TCPMT.2013.2273306},

issn = {2156-3950},

year  = {2013},

date = {2013-08-02},

urldate = {2013-08-02},

journal = {IEEE Transactions on Components, Packaging and Manufacturing Technology},

volume = {3},

number = {12},

pages = {2147-2155},

abstract = {3-D printing allows increased design flexibility in the fabrication of microwave circuits and devices and is reaching a level of maturity that allows for functional parts. Little is known about the RF and microwave properties of the standard materials that have been developed for 3-D printing. This paper measures a wide variety of materials over a broad spectrum of frequencies from 1 MHz to 10 GHz using a variety of well-established measurement methods.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{RN77,

title = {Effects of extreme surface roughness on 3D printed horn antenna},

author = {CR Garcia and RC Rumpf and HH Tsang and JH Barton},

url = {https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/el.2013.1528},

doi = {https://doi.org/10.1049/el.2013.1528},

issn = {1350-911X},

year  = {2013},

date = {2013-06-01},

journal = {Electronics letters},

volume = {49},

number = {12},

pages = {734-736},

abstract = {3D printing is an emerging technology in manufacturing. It is the long-term goal of the industry to print complex and fully functional products from cell phones to vehicles. A drawback of many 3D printing technologies is rough surface finish. It is known that metals with high surface roughness severely degrade the propagation of electromagnetic waves. Presented is the first known evaluation of the electromagnetic impact of the typical surface roughness in metal parts produced by electron beam melting. Two Ku-band (12–15 GHz) horn antennas were 3D printed, with different surface roughness, and compared to a standard horn antenna purchased from Pasternack.},

keywords = {3D printing, electron beam melting, surface finish, surface roughness},

pubstate = {published},

tppubtype = {article}

}

@article{RN74,

title = {Guided-mode resonance filter compensated to operate on a curved surface},

author = {Raymond C Rumpf and Marvin Gates and Carrie L Kozikowski and William A Davis},

url = {https://www.jpier.org/pierc/pier.php?paper=13041209},

doi = {10.2528/PIERC13041209},

issn = {1937-8718},

year  = {2013},

date = {2013-05-23},

journal = {Progress In Electromagnetics Research C},

volume = {40},

pages = {93-103},

abstract = {Guided-mode resonance filters (GMRFs) are highly compact structures that can produce a strong frequency response from a single thin layer of dielectric. When a GMRF is formed onto a curved surface, the local angle of incidence varies over the aperture of the device and the overall performance significantly degrades. In the present work, we spatially varied the grating period of a curved GMRF to perfectly compensate for the local angle of incidence. The performance of the curved device actually surpassed that of a flat device because it also compensated for the spherical wave front from the source. This paper summarizes our design process and experimental results obtained around 25 GHz.},

keywords = {curved surface, GMRF, guided mode resonance (GMR)},

pubstate = {published},

tppubtype = {article}

}

@article{RN73,

title = {Optimization of planar self-collimating photonic crystals},

author = {Raymond C Rumpf and Javier J Pazos},

url = {https://www.osapublishing.org/josaa/abstract.cfm?uri=josaa-30-7-1297#articleBody},

doi = {https://doi.org/10.1364/JOSAA.30.001297},

issn = {1520-8532},

year  = {2013},

date = {2013-05-01},

journal = {JOSA A},

volume = {30},

number = {7},

pages = {1297-1304},

abstract = {Self-collimation in photonic crystals has received a lot of attention in the literature, partly due to recent interest in silicon photonics, yet no performance metrics have been proposed. This paper proposes a figure of merit (FOM) for self-collimation and outlines a methodical approach for calculating it. Performance metrics include bandwidth, angular acceptance, strength, and an overall FOM. Two key contributions of this work include the performance metrics and identifying that the optimum frequency for self-collimation is not at the inflection point. The FOM is used to optimize a planar photonic crystal composed of a square array of cylinders. Conclusions are drawn about how the refractive indices and fill fraction of the lattice impact each of the performance metrics. The optimization is demonstrated by simulating two spatially variant self-collimating photonic crystals, where one has a high FOM and the other has a low FOM. This work gives optical designers tremendous insight into how to design and optimize robust self-collimating photonic crystals, which promises many applications in silicon photonics and integrated optics.},

keywords = {figure of merit, photonic crystals, self-collimation, silicon photonics, spatially variant photonic crystals},

pubstate = {published},

tppubtype = {article}

}

@article{RN17,

title = {Fabrication of metal-oxide nano-hairs for effective index optical elements},

author = {I. R. Srimathi and A. J. Pung and Y. Li and R. C. Rumpf and E. G. Johnson},

doi = {10.1364/oe.21.018733},

issn = {1094-4087},

year  = {2013},

date = {2013-05-01},

journal = {Opt Express},

volume = {21},

number = {16},

pages = {18733-41},

abstract = {We present a method for fabricating high aspect ratio metal-oxide, sub-wavelength grating structures. These "nano-hair" structures are composed of alumina cylindrical pillars, partially embedded in a supporting fused silica substrate. The fabricated nano-hair structures demonstrate phase control of the transmitted beam while maintaining a peak transmitted power greater than 93% around a central wavelength of λ(o) = 1.55 µm. Based on this principle, discrete and continuous phase functions can be encoded by controlling the lithographic process.},

note = {1094-4087 

Srimathi, Indumathi Raghu 

Pung, Aaron J 

Li, Yuan 

Rumpf, Raymond C 

Johnson, Eric G 

Journal Article 

Research Support, U.S. Gov't, Non-P.H.S. 

United States 

2013/08/14 

Opt Express. 2013 Aug 12;21(16):18733-41. doi: 10.1364/OE.21.018733.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{RN82,

title = {Fabrication of metal-oxide nano-hairs for effective index optical elements},

author = {Indumathi Raghu Srimathi and Aaron J Pung and Yuan Li and Raymond C Rumpf and Eric G Johnson},

url = {https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-21-16-18733&id=259842},

issn = {1094-4087},

year  = {2013},

date = {2013-05-01},

journal = {Optics express},

volume = {21},

number = {16},

pages = {18733-18741},

abstract = {We present a method for fabricating high aspect ratio metal-oxide, sub-wavelength grating structures. These “nano-hair” structures are composed of alumina cylindrical pillars, partially embedded in a supporting fused silica substrate. The fabricated nano-hair structures demonstrate phase control of the transmitted beam while maintaining a peak transmitted power greater than 93% around a central wavelength of λ o  = 1.55 µm. Based on this principle, discrete and continuous phase functions can be encoded by controlling the lithographic process.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{RN83,

title = {Printed Circuit Structures, the Evolution of Printed Circuit Boards},

author = {Kenneth H Church and Harvey Tsang and Ricardo Rodriguez and Paul Defembaugh and Raymond Rumpf},

url = {https://www.researchgate.net/publication/260870514_Printed_Circuit_Structures_the_Evolution_of_Printed_Circuit_Boards},

year  = {2013},

date = {2013-02-01},

booktitle = {IPC APEX EXPO Conference Proceedings},

journal = {Proc. IPC Apex EXPO},

volume = {2},

abstract = {The printed circuit board is the backbone of electronics and a large number of consumer devices. The challenge to put more function in a smaller space requires more components utilizing smaller bond pads, smaller lines and tighter pitch. The electronic packaging industry has aggressively pursued novel ways to shrink and stack multilayer boards inside smaller volumes. The industry is approaching serious obstacles in the continued size reduction requirements with the need for wires, epoxy, vias, solder and sometimes bolts and screws to mount the boards. The next logical step is to move beyond 2D stacking, which is 2.5D, to make 3D packages and to utilize the third dimension directly. Eliminate the traditional 2D FR-4 board and the wires, epoxies, vias and solder and make the next-generation packages utilizing 3D: the printed circuit structure (PCS). The PCS concept will allow passives, actives and even antennas to move out of the XY plane and into the XZ and YZ planes. This new dimension will appear to be very complex and next-generation circuit optimization will be required, but the end result will net a significant improvement in volume utilization. In addition, if new materials are developed and utilized properly, the PCS will be the box or the package, thus eliminating all the bolts and screws necessary to mount a PCB in a traditional box or package, saving space and reducing weight. In this paper, nScrypt and the University of Texas at El Paso will present 3D printing of printed circuit structures. A demonstration of true 3D electronic structures will be demonstrated and shown as well as novel approaches that utilize CAD to 3D printing, including the electronics portion.},

keywords = {3D printed circuits, printed circuit structure},

pubstate = {published},

tppubtype = {article}

}

@article{RN70,

title = {3D printed lattices with spatially variant self-collimation},

author = {Raymond C Rumpf and Javier Pazos and Cesar R Garcia and Luis Ochoa and Ryan Wicker},

url = {https://www.jpier.org/PIER/pier139/01.13030507.pdf},

issn = {1070-4698},

year  = {2013},

date = {2013-01-01},

journal = {Progress In Electromagnetics Research},

volume = {139},

pages = {1-14},

abstract = {In this work, results are given for controlling waves arbitrarily inside a lattice with spatially variant self-collimation. To demonstrate the concept, an unguided beam was made to flow around a 90 deg bend without scattering due to the bend or the spatial variance. Control of the field was achieved by spatially varying the orientation of the unit cells throughout a self-collimating photonic crystal, but in a manner that almost completely eliminated deformations to the size and shape of the unit cells. The device was all-dielectric, monolithic, and made from an ordinary dielectric with low relative permittivity (εr = 2.45). It was manufactured by fused deposition modeling, a form of 3D printing, and its performance confirmed experimentally at 

around 15 GHz.},

keywords = {3D printing, self-collimation, spatially variant},

pubstate = {published},

tppubtype = {article}

}

@article{RN71,

title = {All-dielectric frequency selective surfaces with few number of periods},

author = {Jay H Barton and Raymond C Rumpf and Randall W Smith and Carrie L Kozikowski and Phillip A Zellner},

url = {https://www.jpier.org/pierb/pier.php?paper=12042404},

doi = {10.2528/PIERB12042404},

issn = {1937-6472},

year  = {2012},

date = {2012-06-11},

urldate = {2012-06-11},

journal = {Progress In Electromagnetics Research B},

volume = {41},

pages = {269-283},

abstract = {All-dielectric frequency selective surfaces (FSSs) can serve as an alternative to their metallic counterparts when they must operate at very high power, loss must be minimized, or when the surface itself must be low observable. When metals are avoided, there is a weaker interaction with electromagnetic waves and it becomes more difficult to achieve strong suppression in the stop band while also realizing compact size, wide field-of-view or broadband operation. One attractive approach utilizes guided-mode resonance (GMR) as the filtering mechanism, but this phenomenon exhibits several drawbacks that must be overcome for practical application at radio frequencies. This paper introduces the concept of guide-mode resonance for FSSs and describes how they can be made to operate with a dramatically fewer number of periods than conventional GMR devices.},

keywords = {frequency selective surface (FSS), frequency selective surface (FSS), GMR, guided mode resonance (GMR)},

pubstate = {published},

tppubtype = {article}

}

@article{RN51,

title = {Synthesis of spatially variant lattices},

author = {Raymond C Rumpf and Javier Pazos},

url = {https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-20-14-15263&id=239020},

doi = {https://doi.org/10.1364/OE.20.015263},

issn = {1094-4087},

year  = {2012},

date = {2012-04-01},

journal = {Optics express},

volume = {20},

number = {14},

pages = {15263-15274},

abstract = {It is often desired to functionally grade and/or spatially vary a periodic structure like a photonic crystal or metamaterial, yet no general method for doing this has been offered in the literature. A straightforward procedure is described here that allows many properties of the lattice to be spatially varied at the same time while producing a final lattice that is still smooth and continuous. Properties include unit cell orientation, lattice spacing, fill fraction, and more. This adds many degrees of freedom to a design such as spatially varying the orientation to exploit directional phenomena. The method is not a coordinate transformation technique so it can more easily produce complicated and arbitrary spatial variance. To demonstrate, the algorithm is used to synthesize a spatially variant self-collimating photonic crystal to flow a Gaussian beam around a 90° bend. The performance of the structure was confirmed through simulation and it showed virtually no scattering around the bend that would have arisen if the lattice had defects or discontinuities.},

keywords = {photonic crystals, self-collimation, spatially variant lattice},

pubstate = {published},

tppubtype = {article}

}

@article{RN45,

title = {3D printing of anisotropic metamaterials},

author = {Cesar R Garcia and Jesus Correa and David Espalin and Jay H Barton and Raymond C Rumpf and Ryan Wicker and Virgilio Gonzalez},

url = {https://www.jpier.org/PIERL/pierl34/08.12070311.pdf},

issn = {1937-6480},

year  = {2012},

date = {2012-01-01},

journal = {Progress In Electromagnetics Research Letters},

volume = {34},

pages = {75-82},

abstract = {—Material properties in radio frequency and microwave 

regimes are limited due to the lack of molecular resonances at these 

frequencies. Metamaterials are an attractive means to realize a 

prescribed permittivity or permeability function, but these are often 

prohibitively lossy due to the use of inefficient metallic resonators. 

All-dielectric metamaterials offer excellent potential to overcome these 

losses, but they provide a much weaker interaction with an applied 

wave. Much design freedom can be realized from all-dielectric 

structures if their dispersion and anisotropy are cleverly engineered. 

This, however, leads to structures with very complex geometries 

that cannot be manufactured by conventional techniques. In this 

work, artificially anisotropic metamaterials are designed and then 

manufactured by 3D printing. The effective material properties are 

measured in the lab and agree well with model predictions.},

keywords = {3D printing, all-dielectric structures, metamaterials},

pubstate = {published},

tppubtype = {article}

}

@article{RN60,

title = {Creation of three-dimensional micro-photonic structures on the end-face of optical fibers},

author = {Stephen M Kuebler and Henry E Williams and Daniel J Freppon and Raymond C Rumpf and Marco A Melino},

url = {https://stars.library.ucf.edu/facultybib2010/2890/},

year  = {2012},

date = {2012-01-01},

urldate = {2012-01-01},

journal = {Journal of Laser Micro Nanoengineering},

volume = {7},

number = {3},

pages = {293},

abstract = {A process is reported that enables fabrication of truly three-dimensional micro-photonic structures directly onto the end face of an optical fiber by multi-photon direct laser writing in the cross-linkable epoxide SU-8. Solvent-free SU-8 resin is first obtained by heating in vacuo to remove volatiles. The resulting resin solids are then melt-reflowed around an optical fiber in a mold integrated into a sample mount. The resin is allowed to cool and solidify around the optical fiber, so the entire sample mount can be affixed to an optical system for direct laser writing. Using this approach a wide range of refractive and diffractive micro-optical structures can be integrated onto optical fibers that would be difficult, if not impossible, to create by other existing methods. Optical characterization of lens-tipped fibers shows that the approach can be used control the propagation of beams exiting from functionalized fibers, and the performance is reproducible across repeated fabrication of the same device. This work illustrates a new path to fiber-based integrated photonic devices.},

keywords = {Applied, laser materials processing, micro-optics, microstructure fabrication, Multidisciplinary  Optics  Physics, nanophotonics, photonic crystals, SU-8},

pubstate = {published},

tppubtype = {article}

}

@article{RN55,

title = {Azimuthally varying guided mode resonance filters},

author = {Zachary A Roth and Pradeep Srinivasan and Menelaos K Poutous and Aaron J Pung and Raymond C Rumpf and Eric G Johnson},

url = {https://www.mdpi.com/2072-666X/3/1/180},

doi = {https://doi.org/10.3390/mi3010180},

year  = {2012},

date = {2012-01-01},

journal = {Micromachines},

volume = {3},

number = {1},

pages = {180-193},

abstract = {New and novel sensing schemes require optical functions with unconventional spatial light distributions, as well as complex spectral functionality. Micro-optical elements have shown some flexibility in their ability to spatially encode phase information using surface relief dielectrics. In this paper, we present a novel optical component that exploits the properties of optically resonant structures to make an azimuthally spatially varying spectral filter. The dispersive properties are quite unique with an angular resonance shift of 28 Deg/nm. This device is fabricated using techniques that are compatible with standard micro-electronic fabrication technologies.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{RN44,

title = {Simple implementation of arbitrarily shaped total-field/scattered-field regions in finite-difference frequency-domain},

author = {Raymond C Rumpf},

url = {https://www.jpier.org/pierb/pier.php?paper=11092006},

issn = {1937-6472},

year  = {2011},

date = {2011-11-10},

journal = {Progress In Electromagnetics Research},

volume = {36},

pages = {221-248},

abstract = {The total-field/scattered-field (TF/SF) formulation is a popular technique for incorporating sources into electromagnetic models like the finite-difference frequency-domain (FDFD) method. It is versatile and simplifies calculation of waves scattered from a device. In the context of FDFD, the TF/SF formulation involves modifying all of the finite-difference equations that contain field terms from both the TF and SF regions in order to make the terms compatible. While simple in concept, modifying all of the equations for arbitrarily shaped TF/SF regions is tedious and no solution has been offered in the literature to do it in a straightforward manner. This paper presents a simple and efficient technique for implementing the TF/SF formulation that allows the TF/SF regions to be any shape and of arbitrary complexity. Its simplicity and versatility are demonstrated by giving several practical examples including a diffraction grating, a waveguide problem, and a scattering problem with a cylindrical wave source.},

keywords = {finite-difference frequency-domain (FDFD), finite-difference frequency-domain (FDFD), scattered-field, TF/SF, total-field},

pubstate = {published},

tppubtype = {article}

}

@article{RN64,

title = {Improved formulation of scattering matrices for semi-analytical methods that is consistent with convention},

author = {Raymond C Rumpf},

url = {https://www.jpier.org/pierb/pier.php?paper=11083107},

doi = {10.2528/PIERB11083107},

issn = {1937-6472},

year  = {2011},

date = {2011-10-31},

journal = {Progress In Electromagnetics Research B},

volume = {35},

pages = {241-261},

abstract = {The literature describing scattering matrices for semi-analytical methods almost exclusively contains inefficient formulations and formulations that deviate from long-standing convention in terms of how the scattering parameters are defined. This paper presents a novel and highly improved formulation of scattering matrices that is consistent with convention, more efficient to implement, and more versatile than what has been otherwise presented in the literature. Semi-analytical methods represent a device as a stack of layers that are uniform in the longitudinal direction. Scattering matrices are calculated for each layer and are combined into a single overall scattering matrix that describes propagation through the entire device. Free space gaps with zero thickness are inserted between the layers and the scattering matrices are made to relate fields which exist outside of the layers, but directly on their boundaries. This framework produces symmetric scattering matrices so only two parameters need to be calculated and stored instead of four. It also enables the scattering matrices to be arbitrarily interchanged and reused to describe longitudinally periodic devices more efficiently. Numerical results are presented that show speed and efficiency can be increased by more than an order of magnitude using the improved formulation.},

keywords = {scattering matrices, semi-analytical methods},

pubstate = {published},

tppubtype = {article}

}

@article{RN46,

title = {Two-dimensional guided mode resonance filters fabricated in a uniform low-index material system},

author = {Aaron J Pung and Menelaos K Poutous and Raymond C Rumpf and Zachary A Roth and Eric G Johnson},

url = {https://www.osapublishing.org/ol/abstract.cfm?uri=ol-36-16-3293},

doi = {https://doi.org/10.1364/OL.36.003293},

issn = {1539-4794},

year  = {2011},

date = {2011-06-01},

urldate = {2011-06-01},

journal = {Optics letters},

volume = {36},

number = {16},

pages = {3293-3295},

abstract = {We demonstrate the fabrication, simulation, and experimental results of a buried, homogeneous narrowband spectral filter with a periodic, hexagonal unit cell of air pockets, encapsulated in a fused silica substrate. The leaky waveguide is formed by depositing  SiO},

keywords = {diffraction gratings, guided mode resonance (GMR), homogeneous narrowband spectral filter, phase matching},

pubstate = {published},

tppubtype = {article}

}

@article{RN36,

title = {Fabrication of three-dimensional micro-photonic structures on the tip of optical fibers using SU-8},

author = {Henry E Williams and Daniel J Freppon and Stephen M Kuebler and Raymond C Rumpf and Marco A Melino},

url = {https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-19-23-22910&id=224017},

doi = {https://doi.org/10.1364/OE.19.022910},

issn = {1094-4087},

year  = {2011},

date = {2011-01-01},

journal = {Optics express},

volume = {19},

number = {23},

pages = {22910-22922},

abstract = {A method is reported for fabricating truly three-dimensional micro-photonic structures directly onto the end face of an optical fiber using the cross-linkable resist SU-8. This epoxide-based material is well suited for micro-device fabrication because it is photo-processed as a solid and the cross-linked material is mechanically robust, chemically resistant, and optically transparent. Yet, procedures commonly used to process SU-8, particularly spin-coating, are impractical when the intended fabrication substrate is the end-face of an optical fiber. A melt-reflow process was developed to prepare optical fibers having SU-8 resin deposited at controlled thickness on the fiber end-face. Multi-photon direct laser writing was then used to fabricate various refractive lenses, a compound lens system, and a woodpile photonic crystal within the resin on the end-face of the optical fiber. Data are presented that show how the refractive lenses can be used to alter the output of the optical fiber. This work opens a new path to low-profile integrated photonic devices.},

keywords = {3D micro-photonic structures, low-profile integrated photonic devices, multi-photon direct laser writing, optical fiber},

pubstate = {published},

tppubtype = {article}

}

@article{RN57,

title = {Micro-optical spatial and spectral elements},

author = {Pradeep Srinivasan and Yigit Ozan Yilmaz and Raymond C Rumpf and Eric G Johnson},

url = {https://www.spiedigitallibrary.org/journals/optical-engineering/volume-48/issue-11/110501/Micro-optical-spatial-and-spectral-elements/10.1117/1.3258651.full?SSO=1},

doi = {https://doi.org/10.1117/1.3258651},

issn = {0091-3286},

year  = {2009},

date = {2009-11-01},

journal = {Optical Engineering},

volume = {48},

number = {11},

pages = {110501},

abstract = {Interference filters have a defect layer incorporated within a photonic crystal structure and generate a narrow transmission notch within a wide stop band. In this paper, we propose and demonstrate wavelength-tunable spatial filters by introducing diffractive optical elements in the defect layer. The spectral transmission through the device was a function of the local defect layer thickness under broadband illumination. For each wavelength, the spatial transmission followed the contours of equal defect layer optical thickness. The devices were implemented by depositing a one-dimensional photonic crystal with a centrally integrated defect layer on a silicon substrate using plasma-enhanced chemical vapor deposition. The defect layer was lithographically patterned with charge 2, 8-level vortex structures. The spectral transmission peak and linewidth was characterized by separately illuminating each zone of diffractive element using a tunable laser source and compared with model simulations. The spatial transmission through the device was imaged onto a CCD camera. Triangular wedge-shaped zones with wavelength-dependent orientations were observed. These novel devices with spectrally tunable spatial transmission have potential applications in pupil filtering, hyperspectral imaging, and engineered illumination systems.},

keywords = {image filtering, optical filters, photonic crystals, spatial filters},

pubstate = {published},

tppubtype = {article}

}

@article{RN32,

title = {Spatial and spectral beam shaping with space-variant guided mode resonance filters},

author = {Pradeep Srinivasan and Menelaos K Poutous and Zachary A Roth and Yigit O Yilmaz and Raymond C Rumpf and Eric G Johnson},

url = {https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-17-22-20365&id=188249},

doi = {https://doi.org/10.1364/OE.17.020365},

issn = {1094-4087},

year  = {2009},

date = {2009-05-01},

journal = {Optics express},

volume = {17},

number = {22},

pages = {20365-20375},

abstract = {Novel all-dielectric beam shaping elements were developed based on guided mode resonance (GMR) filters. This was achieved by spatially varying the duty cycle of a hexagonal-cell GMR filter, to locally detune from the resonant condition, which resulted in modified wavelength dependent reflection and transmission profiles, across the device aperture. This paper presents the design, fabrication, and characterization of the device and compares simulations to experimental results.},

keywords = {beam shaping, GMR, guided mode resonance (GMR), narrow band filters},

pubstate = {published},

tppubtype = {article}

}

@article{RN68,

title = {Biologically inspired optics: analog semiconductor model of the beetle exoskeleton},

author = {Kaia Buhl and Zachary Roth and Pradeep Srinivasan and Raymond Rumpf and Eric Johnson},

url = {https://www.spiedigitallibrary.org/conference-proceedings-of-spie/7057/1/Biologically-inspired-optics--analog-semiconductor-model-of-the-beetle/10.1117/12.794313.short},

doi = {https://doi.org/10.1117/12.794313},

year  = {2008},

date = {2008-08-11},

booktitle = {The Nature of Light: Light in Nature II},

volume = {7057},

pages = {705707},

publisher = {International Society for Optics and Photonics},

abstract = {Evolution in nature has produced through adaptation a wide variety of distinctive optical structures in many life forms. For example, pigment differs greatly from the observed color of most beetles because their exoskeletons contain multilayer coatings. The green beetle is disguised in a surrounding leaf by having a comparable reflection spectrum as the leaves. The Manuka and June beetle have a concave structure where light incident at any angle on the concave structures produce matching reflection spectra. In this work, semiconductor processing methods were used to duplicate the structure of the beetle exoskeleton. This was achieved by combining analog lithography with a multilayer deposition process. The artificial exoskeleton, 3D concave multilayer structure, demonstrates a wide field of view with a unique spectral response. Studying and replicating these biologically inspired nanostructures may lead to new knowledge for fabrication and design of new and novel nano-photonic devices, as well as provide valuable insight to how such phenomenon is exploited.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}