Donald B. Adams

Vertically integrated As2S3 ring resonator on LiNbO3

Titanium-diffused lithium niobate (Ti:LiNbO(3)) waveguides are widely used in current fiber optic networks because of their high-speed, electro-optic modulation, and low-loss integration with standard single-mode fibers. However, they cannot achieve small ring resonators owing to their lack of a high core-to-cladding index contrast. To overcome this challenge, we vertically integrate an emerging chalcogenide glass waveguide technology on well-established Ti:LiNbO(3) waveguides. We present, to our knowledge, the first arsenic trisulfide (As(2)S(3)) race-track ring resonator with a 290.8 microm bend radius in an all-pass filter configuration, integrated on a Ti:LiNbO(3) waveguide. Vertical coupling is achieved using a unique taper design. Experimental results are shown for 10.6% coupling, 2.08 dB roundtrip loss, and a 25.4 GHz free-spectral range.

A Novel Broadband Photonic RF Phase Shifter

A novel broadband photonic RF phase shifter is proposed that employs single-sideband modulation of the broadband RF signal onto an optical carrier. The phase of the carrier is shifted relative to the modulated signal using an optical allpass filter. Ring-resonator-based optical allpass filters are tuned across the carrier frequency to yield an RF phase shift of over 360 degrees. Results from a proof-of-concept experimental demonstration are presented for modulation frequencies in the range of 2-4 GHz.

Compact Bends for Achieving Higher Integration Densities for LiNbO

A new waveguide platform is demonstrated that allows the bend radii to be substantially decreased for titanium-diffused lithium-niobate (LiNbO3) waveguides using vertically integrated arsenic-trisulfide (As2S3) overlay waveguides. Power is transferred from a Ti-diffused waveguide into the overlay waveguide using tapers, guided by the As2S3 waveguide through the S-bend region and transferred back into another Ti-diffused waveguide. This structure also behaves like a polarization beam splitter. We present simulation results as well as measurements to show the feasibility of achieving low loss and reduced bend radii for electrooptic waveguides.

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The NLFM waveform resulting from a tunable integrated optical ring resonator is simulated and compared with the well known tan-FM waveform. The metrics of interest are the first sidelobe levels and FWHM times of the autocorrelation, as these directly relate to the long-range performance and fine range resolution of a LADAR system, and should ideally be as small as possible. Through simulation, the sidelobe level of the autocorrelation of an NLFM waveform generated by a series of tunable integrated optical ring resonators is shown to be lower than the autocorrelation sidelobe level of an equivalent optimized tan-FM waveform with an equal FWHM time. A proof of concept experiment employing thermally tunable Silicon Nitride integrated optical ring resonator is shown to generate NLFM chirped waveforms with frequency chirps of 28 kHz.

Waveguides

The Jones matrix measured with an optical vector analyzer (OVA) is the result of a cascade of individual Jones matrices representing the input fiber path, device under test (DUT), and output fiber path. To extract the DUT matrix, compensation of the random polarization rotation on the Poincaré sphere caused by the input and output fiber is necessary. In this letter, we present a novel algorithm that factors out the Jones matrix of the fiber pigtails and enables the DUT matrix to be resolved in a convenient reference frame. A mathematical description of the algorithm is presented and the algorithm is verified by measuring a wave plate and a polarization converter. The efficacy of the algorithm is demonstrated through characterization of a microring resonator (MRR) including round-trip loss, ring-bus coupling coefficient, and group delay of each polarization beyond the magnitude response represented by Q-factor.

A novel NLFM waveform generator using tunable integrated optical ring resonators: simulation and proof of concept experiment

A high-resolution measurement to characterize the optical amplitude and phase is presented that uses single sideband modulation, a swept-wavelength tunable laser, and a Mach-Zehnder interferometer for frequency offset accuracy.

Device-Under-Test Jones Matrix Extraction Algorithm With Device TE/TM Reference Frame

The NLFM waveform resulting from a tunable integrated optical ring resonator is simulated. The metrics of interest are the first sidelobe levels and FWHM times of the autocorrelation, as these directly relate to the long-range performance and fine range resolution of a LADAR system, and should ideally be as small as possible. Through simulation, the maximum sidelobe level of the autocorrelation of an NLFM waveform generated by a series of tunable integrated optical ring resonators is shown to be -20 to -30 dB or lower. A proof of concept experiment employing an off-the-shelf thermally tunable silicon-nitride optical ring resonator is shown to generate NLFM chirped waveforms with a bandwidth of 28 kHz.

High Resolution Optical Phase Response Measurement Using Single Sideband Modulation

A technique using a tunable dispersive filter is presented to obtain the relative phase and amplitude of a periodic optical waveform. A proof-of-concept demonstration is presented using a dual-drive modulator to create modulated test signals. The experimental results of their characterization are presented and compared to theory.

NLFM waveform generation using tunable integrated optical ring resonators: simulation and proof of concept experiment

A fast, non-interferometric measurement technique that allows the frequency-dependent delay and amplitude responses to be measured is presented. For a single amplitude and relative phase measurement at a fixed optical wavelength, the measurement time is on the order of a microsecond. RF modulation up to 2.7 GHz can be accommodated. A modified technique using frequency modulation is described to overcome non-idealities in the phase measurement. Results are presented for a fiber Bragg grating and an acetylene gas cell with swept-wavelength laser tuning at a rate of 40 nm/s.

Complex Optical Spectrum Analysis Using a Tunable Dispersive Optical Filter

A boundless-range phase shifter is demonstrated at 10GHz using a dual parallel electro-optic modulator. Sideband and carrier rejections over 30dB are achieved using a coherent optical spectrum analyzer to verify the operation.