Charles Williams

A spectrally efficient multiheterodyne scheme is applied for the independent measurement of the spectral phase profiles of three distinct semiconductor frequency combs. The amount of quadratic and cubic phase is quantified for each source, providing insight on the dispersive properties of the semiconductor gain and the fiberized laser cavity. This information is vital for the optimization and expansion of the spectral bandwidth of such sources.

Waveguide coupling to closed loop coupled-resonator optical waveguides is explored. By coupling a CROW chain back on itself, a reduction in individual resonant linewidth is achieved making these slow light modes more conducive to periodic filters toward novel frequency-comb integration. Through numerical simulation by finite-difference time-domain methods, the importance of waveguide symmetry conditions for coupling is illustrated. The impact of unit cavity mode symmetry strongly impacts the… Show more

Waveguide coupling to closed loop coupled-resonator optical waveguides is explored. By coupling a CROW chain back on itself, a reduction in individual resonant linewidth is achieved making these slow light modes more conducive to periodic filters toward novel frequency-comb integration. Through numerical simulation by finite-difference time-domain methods, the importance of waveguide symmetry conditions for coupling is illustrated. The impact of unit cavity mode symmetry strongly impacts the necessary coupling geometry to both cavities and waveguides. Design insight into different waveguide coupling schemes is provided while aiming to achieve transmission of the resonant structure exhibited by the isolated resonator. Show less

Coupled Mode Theory analysis of a new architecture for coupled-resonance optical waveguide design is presented that enables a feedback mechanism in a photonic crystal scheme while also increasing resonant finesse from 2.77 to 10.15.

Extensive noise analysis is presented of a semiconductor-based coupled opto-electronic oscillator using continuous-wave optical injection for the generation of an optical frequency comb with 10.24 GHz spacing. The suppression of unwanted optical axial mode groups arising from the harmonic nature of mode locking is achieved via gain competition. Amplitude noise measurements show a marked reduction in noise due to optical injection for multiple injection powers. Supermode noise spur suppression… Show more

Extensive noise analysis is presented of a semiconductor-based coupled opto-electronic oscillator using continuous-wave optical injection for the generation of an optical frequency comb with 10.24 GHz spacing. The suppression of unwanted optical axial mode groups arising from the harmonic nature of mode locking is achieved via gain competition. Amplitude noise measurements show a marked reduction in noise due to optical injection for multiple injection powers. Supermode noise spur suppression is shown to be greater than 15 dB in absolute phase noise measurements, taken using the frequency discriminator technique. Allan deviation measurements are also shown for both the free-running and injection-locked states. Show less

Optical frequency combs are used as local oscillators for the measurement and analysis of unknown optical waveforms with periodic time domain structures. Experimental results obtained by heterodyning pulsed and phase-modulated laser sources are presented. The analysis is then extended to the heterodyning and sampling of bandlimited incoherent light sources. It is shown theoretically and experimentally that the correlations between photodetected white light at different times can generate RF… Show more

Optical frequency combs are used as local oscillators for the measurement and analysis of unknown optical waveforms with periodic time domain structures. Experimental results obtained by heterodyning pulsed and phase-modulated laser sources are presented. The analysis is then extended to the heterodyning and sampling of bandlimited incoherent light sources. It is shown theoretically and experimentally that the correlations between photodetected white light at different times can generate RF interference that is sensitive to the optical phase. Show less

This work presents an extensive investigation of the performance characteristics of a semiconductor-based Theta cavity design laser with an intra-cavity Fabry-Pérot etalon operating at 100 MHz repetition rate. The Theta laser being an external cavity harmonically mode-locked semiconductor laser exhibits supermode noise that impairs its performance. A fiberized Fabry-Pérot periodic filter inserted within the Theta laser cavity mitigates the contribution of the supermode noise to the… Show more

This work presents an extensive investigation of the performance characteristics of a semiconductor-based Theta cavity design laser with an intra-cavity Fabry-Pérot etalon operating at 100 MHz repetition rate. The Theta laser being an external cavity harmonically mode-locked semiconductor laser exhibits supermode noise that impairs its performance. A fiberized Fabry-Pérot periodic filter inserted within the Theta laser cavity mitigates the contribution of the supermode noise to the pulse-to-pulse energy variance by 20 times. The laser has both a compressed output with picosecond pulse duration and a uniform intensity quasi-CW linearly chirped pulse output with 10 nm bandwidth. Long-term stability is attained by referencing the cavity length to the etalon using an intra-cavity Hänsch-Couillaud locking scheme. Show less

A low-noise, chirped-pulse diode-laser design reduces costs compared to conventional laser designs and thus facilitates a broad range of information, sensing, and photonic applications.

We report a frequency-stabilized semiconductor-based mode-locked laser that uses a phase modulator and an intracavity Fabry-Perot etalon for both active mode-locking and optical frequency stabilization. A twofold multiplication of the repetition frequency of the laser is inherently obtained in the process. The residual timing jitter of the mode-locked pulse train is 13fs ( 1Hz to 100MHz ), measured after regenerative frequency division of the photo detected pulse train.

A novel method is presented to provide long-term stabilization of an injection-locked harmonically mode-locked laser to a narrow linewidth continuous-wave (CW) source for the first time. The method, based on the Pound-Drever-Hall method of laser frequency stabilization, exploits the phase shift across a laser cavity mode resonance to detect the offset between the CW frequency and the combline frequency desired for injection-locking. Longterm suppression of the radio-frequency supermode noise… Show more

A novel method is presented to provide long-term stabilization of an injection-locked harmonically mode-locked laser to a narrow linewidth continuous-wave (CW) source for the first time. The method, based on the Pound-Drever-Hall method of laser frequency stabilization, exploits the phase shift across a laser cavity mode resonance to detect the offset between the CW frequency and the combline frequency desired for injection-locking. Longterm suppression of the radio-frequency supermode noise spurs is shown as well as 36-dB suppression of optical supermodes. Significant reductions in phase and amplitude noise are also shown due to injection. Postamplification noise results are presented, showing an increase in optical power per combline with no degradation in pulse-to-pulse energy fluctuation or timing jitter. Show less

A coupled optoelectronic oscillator (COEO) based on a laser with a high finesse intracavity etalon is presented. Unlike a conventional COEO, the incorporation of the etalon produces a 10.24-GHz spaced optical frequency comb by selecting a single optical supermode. The same etalon serves as a reference for active stabilization of the optical frequencies and the pulse repetition rate via the Pound-Drever-Hall stabilization method. This results in 160 to 190 comb lines with sub-1-MHz drift and… Show more

A coupled optoelectronic oscillator (COEO) based on a laser with a high finesse intracavity etalon is presented. Unlike a conventional COEO, the incorporation of the etalon produces a 10.24-GHz spaced optical frequency comb by selecting a single optical supermode. The same etalon serves as a reference for active stabilization of the optical frequencies and the pulse repetition rate via the Pound-Drever-Hall stabilization method. This results in 160 to 190 comb lines with sub-1-MHz drift and sub-10-kHz linewidth, as well as subpicosecond pulses and 350-Hz maximum deviation of the pulse repetition rate over 10 min. The completely self-contained source allows the COEO utility to extend to a host of new coherent communication and signal processing applications. Show less