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Research Interests:
Research Interests:
Research Interests:
Research Interests:
ABSTRACT With the advent of metamaterials has come an unprecedented ability to manipulate and engineer the index of refraction, n, and impedance, Z of materials. Engineering these far field properties has led to exciting developments such... more
ABSTRACT With the advent of metamaterials has come an unprecedented ability to manipulate and engineer the index of refraction, n, and impedance, Z of materials. Engineering these far field properties has led to exciting developments such as negative index materials, electromagnetic cloaks, and perfect lensing. However, metamaterials can also be used to engineer designer microscopic charge distributions, current distributions, and polarizabilities. For instance, the on-resonance charge distribution in the capacitive gap of a split ring resonator (SRR) creates a localized region of high electric field enhancement that has seen prominent application in recent work. Here, we present a method to tune the magnitude of this resonant electric field enhancement. Via structural manipulation of the coupling between the SRR and a non-resonant closed conducting ring, we are able to increase and decrease the oscillator strength of the SRR and thus the field enhancement in the SRR's capacitive gap. We present numerical simulations and experimental measurements at terahertz frequencies to confirm this result.
... Cited By in Scopus (0). Permissions & Reprints. Optical characterization of micro and nanomechanical systems in two dimensions. Hüseyin Rahmi Seren a and Hakan Ürey Corresponding Author Contact Information , a , E-mail The... more
... Cited By in Scopus (0). Permissions & Reprints. Optical characterization of micro and nanomechanical systems in two dimensions. Hüseyin Rahmi Seren a and Hakan Ürey Corresponding Author Contact Information , a , E-mail The Corresponding Author [Author vitae]. ...
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ABSTRACT Particle surface plasmons (PPSs) at visible wavelengths continue to be actively investigated with the goal of nanoscale control of light. In contrast, terahertz (THz) surface plasmon experiments are at a nascent stage of... more
ABSTRACT Particle surface plasmons (PPSs) at visible wavelengths continue to be actively investigated with the goal of nanoscale control of light. In contrast, terahertz (THz) surface plasmon experiments are at a nascent stage of investigation. Doped semiconductors with proper carrier density and mobility support THz PSPs. One approach is to utilize thick doped films etched into subwavelength disks. Given the ease of tuning the semiconductor carrier density, THz PSPs are tunable and exhibit interesting nonlinear THz plasmonic effects. We created THz PSP structures using MBE grown 2um thick InAs films with a doping concentration of 1e17cm−3 on 500um thick semi-insulating GaAs substrate. We patterned 40um diameter disks with a 60um period by reactive ion etching. Our THz time-domain measurements reveal a resonance at 1.1THz which agrees well with simulation results using a Drude model. A nonlinear response occurs at high THz electric field strengths (\textgreater 50kV/cm). In particular, we observed a redshift and quenching of the resonance due to impact ionization which resulted in changes in the carrier density and effective mass due to inter-valley scattering.
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The development of responsive metamaterials has enabled the realization of compact tunable photonic devices capable of manipulating the amplitude, polarization, wave vector, and frequency of light. Integration of semiconductors into the... more
The development of responsive metamaterials has enabled the realization of compact tunable photonic devices capable of manipulating the amplitude, polarization, wave vector, and frequency of light. Integration of semiconductors into the active regions of metallic resonators is a proven approach for creating nonlinear metamaterials through optoelectronic control of the semiconductor carrier density. Metal-free subwavelength resonant semiconductor structures offer an alternative approach to create dynamic metamaterials. We present InAs plasmonic disk arrays as a viable resonant metamaterial at terahertz frequencies. Importantly, InAs plasmonic disks exhibit a strong nonlinear response arising from electric field induced intervalley scattering resulting in a reduced carrier mobility thereby damping the plasmonic response. We demonstrate nonlinear perfect absorbers configured as either optical limiters or saturable absorbers, including flexible nonlinear absorbers achieved by transferri...
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Research Interests:
ABSTRACT Particle surface plasmons (PPSs) at visible wavelengths continue to be actively investigated with the goal of nanoscale control of light. In contrast, terahertz (THz) surface plasmon experiments are at a nascent stage of... more
ABSTRACT Particle surface plasmons (PPSs) at visible wavelengths continue to be actively investigated with the goal of nanoscale control of light. In contrast, terahertz (THz) surface plasmon experiments are at a nascent stage of investigation. Doped semiconductors with proper carrier density and mobility support THz PSPs. One approach is to utilize thick doped films etched into subwavelength disks. Given the ease of tuning the semiconductor carrier density, THz PSPs are tunable and exhibit interesting nonlinear THz plasmonic effects. We created THz PSP structures using MBE grown 2um thick InAs films with a doping concentration of 1e17cm−3 on 500um thick semi-insulating GaAs substrate. We patterned 40um diameter disks with a 60um period by reactive ion etching. Our THz time-domain measurements reveal a resonance at 1.1THz which agrees well with simulation results using a Drude model. A nonlinear response occurs at high THz electric field strengths (\textgreater 50kV/cm). In particular, we observed a redshift and quenching of the resonance due to impact ionization which resulted in changes in the carrier density and effective mass due to inter-valley scattering.
Research Interests:
ABSTRACT Development of tunable, dynamic, and broad bandwidth metamaterial designs is a keystone objective for metamaterials research, necessary for the future viability of metamaterial optics and devices across the electromagnetic... more
ABSTRACT Development of tunable, dynamic, and broad bandwidth metamaterial designs is a keystone objective for metamaterials research, necessary for the future viability of metamaterial optics and devices across the electromagnetic spectrum. Yet, overcoming the inherently localized, narrow bandwidth, and static response of resonant metamaterials continues to be a challenging endeavor. Resonant perfect absorbers have flourished as one of the most promising metamaterial devices with applications ranging from power harvesting to terahertz imaging. Here, an optically modulated resonant perfect absorber is presented. Utilizing photo-excited free carriers in silicon pads placed in the capacitive gaps of split ring resonators, a dynamically modulated perfect absorber is designed and fabricated to operate in reflection. Large modulation depth (38% and 91%) in two absorption bands (with 97% and 92% peak absorption) is demonstrated, which correspond to the LC (0.7 THz) and dipole (1.1 THz) modes of the split ring resonators.
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... Cited By in Scopus (0). Permissions & Reprints. Optical characterization of micro and nanomechanical systems in two dimensions. Hüseyin Rahmi Seren a and Hakan Ürey Corresponding Author Contact Information , a , E-mail The... more
... Cited By in Scopus (0). Permissions & Reprints. Optical characterization of micro and nanomechanical systems in two dimensions. Hüseyin Rahmi Seren a and Hakan Ürey Corresponding Author Contact Information , a , E-mail The Corresponding Author [Author vitae]. ...
Research Interests:
Research Interests:
ABSTRACT With the advent of metamaterials has come an unprecedented ability to manipulate and engineer the index of refraction, n, and impedance, Z of materials. Engineering these far field properties has led to exciting developments such... more
ABSTRACT With the advent of metamaterials has come an unprecedented ability to manipulate and engineer the index of refraction, n, and impedance, Z of materials. Engineering these far field properties has led to exciting developments such as negative index materials, electromagnetic cloaks, and perfect lensing. However, metamaterials can also be used to engineer designer microscopic charge distributions, current distributions, and polarizabilities. For instance, the on-resonance charge distribution in the capacitive gap of a split ring resonator (SRR) creates a localized region of high electric field enhancement that has seen prominent application in recent work. Here, we present a method to tune the magnitude of this resonant electric field enhancement. Via structural manipulation of the coupling between the SRR and a non-resonant closed conducting ring, we are able to increase and decrease the oscillator strength of the SRR and thus the field enhancement in the SRR's capacitive gap. We present numerical simulations and experimental measurements at terahertz frequencies to confirm this result.
Research Interests:
Research Interests:
Research Interests:
Research Interests: Finite element method, Microelectromechanical systems, Long-baseline optical interferometry, High performance, Spectrum, and 12 moreInfrared, Fourier Transform spectroscopy, Optical MEMS, IR Spectroscopy, Diffraction Gratings, Electrostatic Actuator, Electrical And Electronic Engineering, Diffraction Grating, Spectral Resolution, IR Detector, Resonant Frequency, and Fourier transform infrared
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Research Interests:
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Lamellar grating interferometers (LGI) offer compact spectrometer architecture with high spectral resolution and large clear aperture. This study investigates the diffraction based inherent limitations of LGI spectrometers in contrary to... more
Lamellar grating interferometers (LGI) offer compact spectrometer architecture with high spectral resolution and large clear aperture. This study investigates the diffraction based inherent limitations of LGI spectrometers in contrary to conventional Michelson type spectrometer architecture. Simulations and experiments were conducted to demonstrate and explain periodic nature of the interferogram envelope due to Talbot image formation. Simulations reveal that grating period
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ABSTRACT We present optically tunable metamaterials (MMs) on flexible polymer sheets operating at terahertz (THz) frequencies. The flexible MMs, consisting of electric split-ring resonators (eSRRs) on patterned GaAs patches, were... more
ABSTRACT We present optically tunable metamaterials (MMs) on flexible polymer sheets operating at terahertz (THz) frequencies. The flexible MMs, consisting of electric split-ring resonators (eSRRs) on patterned GaAs patches, were fabricated on a thin polyimide layer using a transfer technique. Optical excitation of the GaAs patches modifies the metamaterial response. Our experimental results revealed that, with increasing fluence, a transmission modulation depth of ~ 60% was achieved at the LC resonant frequency of 0.98 THz. In addition, a similar modulation depth was obtained over a broad range from 1.1 to 1.8 THz. Numerical simulations agree with experiment and indicate efficient tuning of the effective permittivity of the MMs. Our flexible tunable device paves the way to create multilayer nonplanar tunable electromagnetic composites for nonlinear and multifunctional applications, including sensing, modulation, and energy harvesting.
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Research Interests:
A novel MEMS stage using one set of comb fingers, capable of 2-axis motion is designed and developed. With an integrated 1.1 mm square microlens-array it deflects 40 um in-plane at 60 V and 95 um out-of-plane at 100 V.