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We highlight the importance of the delay arising from optical filters in slow-light-based microwave phase shifting systems. We calculate the filter delay numerically from the measured amplitude response by using the well-known Kramers–Kronig relations. The complex filter transmission response is then incorporated within a numerical model with which we explain phase shifting results obtained from experiments employing semiconductor optical amplifiers as slow light elements.

We report highly efficient four wave mixing in a GaInP photonic crystal waveguide. Owing to its large bandgap, the ultrafast Kerr nonlinearity of GaInP is not diminished by two photon absorption and related carrier effects for photons in the 1550 nm range. A four-wave-mixing efficiency of -49 dB was demonstrated for cw pump and probe signals in the milliwatt range, while for pulsed pumps with a peak power of 25 mW the conversion efficiency increased to -36 dB. Measured conversion efficiency dependencies on pump probe detuning and on pump power are in excellent agreement with a simple analytical model from which the nonlinear parameter gamma is extracted. Gamma scales approximately with the square of the slow down factor and varies from 800 W(-1) m(-1) at a pump wavelength lambda(p)=1532 nm to 2900 W(-1) m(-1) at lambda(p)=1550 nm. These values are consistent with those obtained from self phase modulation experiments in similar devices.

We demonstrate experimentally and describe analytically two important noise contributions in saturated semiconductor optical amplifiers. The first is spontaneous emission power enhancement that is due to the increased and spatially dependent inversion factor. The second is caused by a nonlinear interaction between the saturating signal and the amplifier noise that, in the optical domain, causes a distinct modification of the noise spectrum over a narrow bandwidth. This modification manifests itself as a noise power decrease in the detected electronic domain.

We present a novel method for the generation of synchronized short pulses at high repetition rates from Er-doped silica fiber lasers. The method employs coupling of an optical pulse train to a passively mode-locked fiber laser. The injected signal repetition rate is slightly detuned from the modal spacing of the fiber laser, such that a subset of the latter modes is injection locked, yielding a high-repetition-rate pulse train. By injecting a 2-GHz train of relatively broad optical pulses at an average power of 100 μW, we achieved a train of 6-ps pulses at rates of 40 GHz from the harmonically locked fiber laser.

Harmonic injection locking can generate pulse trains at high repetition rates from passively mode-locked lasers. We have examined experimentally the mutual interaction of noise with the locking process. For injected signals with large timing and amplitude noise, the mode-locked fiber laser generated a pulse train with reduced noise. Injected signals with low timing and amplitude noise were employed for the reduction of the internal noise of the passively mode-locked laser. The achieved output pulse-to-pulse timing jitter in the range of 20-2500 Hz was ~0.6 ps, comparable with that of actively stabilized fiber lasers.

Pure phase-modulation mode locking of an extended-cavity semiconductor laser, operating near 1.5 microm, is demonstrated. The mode-locked laser uses a two-section optical amplifier that provides both gain and phase modulation.

We report an experimental characterization of additive noise from a single-stage phase shifter based on slow and fast light propagation in a bulk semiconductor optical amplifier. We examine the influence of redshifted sideband suppression and optical input power on the signal-to-noise ratio (SNR) of the detected signal. We conclude that in spite of the up to a 6 dB reduction in the detected noise, the SNR remains dominated by the decrease in the detected signal power.

We demonstrate a direct correspondence between FM parameters used in a frequency-locked loop that is based on multifield FM spectroscopy and the stability of a small-scale coherent population trapping atomic clock. Optimized FM parameters lead to an Allan deviation of 2.8 x 10(-11)/square root tau, while the clock stability deteriorates in a predictable manner for the other FM parameters.

A self-starting optical pulse source based on mutually coupled optoelectronic oscillators is described. The system employs a phototransistor-based microwave oscillator that is coupled to a fiber cavity optoelectronic oscillator with an intracavity fiber parametric amplifier. It self-starts and exhibits 3 ps pulses at a rate of 10 GHz with extremely low jitter of 30, 29, and 40 fs (for integration bandwidths of 100 Hz–15 kHz, 500 Hz–1 MHz, and 100 Hz–1 MHz, respectively).

We describe ultrawideband Raman-mediated wavelength conversion. The nonlinear conversion transfer function is calculated analytically and simulated numerically in the cw regime, and the predicted performance is confirmed experimentally. Data conversion from long- to short-wavelength bands with signal reshaping and significant noise reduction are demonstrated experimentally at 10 Gbits/s and modeled by numerical simulations. Q factors and extinction ratios that are both larger than 10 dB are possible over an effective conversion bandwidth of 35 nm.

We report on a chip scale parametric amplifier based on a GaInP photonic crystal waveguide. The amplifier operates with both pump and signal in the 1550 nm wavelength range and offers an on-chip gain of 11 dB (5 dB including the 6 dB coupling losses) when pumped at only 800 mW. It enables us, therefore, to incorporate the many advantages of parametric amplification within photonic chips for optical communication applications.

We describe time domain characterizations of dynamic four-wave mixing in a low loss modified W1 GaInP photonic crystal waveguide. Using 32 ps wide pump pulses with peak powers of up to 1.1 W we achieved a very large conversion efficiency of -6.8 dB as well as a 1.3 dB parametric gain experienced by a weak CW probe signal. Time domain simulations confirm quantitatively all the measured results.

We investigate four-wave mixing (FWM) in GaInP 1.5 mm long dispersion engineered photonic crystal waveguides. We demonstrate an 11 nm FWM bandwidth in the CW mode and a conversion efficiency of -24 dB in the quasi-CW mode. For picosecond pump and probe pulses, we report a 3 dB parametric gain and nearly a -5 dB conversion efficiency at watt-level peak pump powers.

Summary form only given. The simultaneous operation of a passively mode-locked laser at two different wavelengths is important as a source for high-pulse-rate, wavelength-division multiplexing (WDM) schemes, for wideband pump probe and four-wave mixing experiments. Using the recently introduced harmonic injection-locking scheme, we achieved synchronized locking of a passively mode-locked fiber laser, at two wavelengths (1.53 /spl mu/m and 1.55 /spl mu/m) simultaneously, producing pulses of several picoseconds with 7.5-GHz pulse repetition rates. Because the same scheme can also serve as a storage ring, this work demonstrates the feasibility of a two-color memory ring.

We report what is to our knowledge the first observation of synchronous coherent injection locking of an actively mode-locked extended cavity semiconductor laser to an external light pulse train. In the temporal domain, we observed experimentally and verified theoretically a significant narrowing of the output pulse of the mode-locked laser. In the spectral domain, we demonstrated experimentally the narrowing of the output optical spectrum that was due to rejection of spectral components outside the spectral band of the locking pulses. Locking ranges, in the time and the frequency domains, were measured to be ~200 ps and ~5 nm, respectively.

We report a self-starting passively mode-locked soliton source generating 1-ps-wide pulses. The laser is configured as a ring with an erbium-doped fiber gain medium, a length of conventional fiber that provides the required dispersion and Kerr nonlinearity, and an intracavity multiple-quantum-well optical amplifier that serves as a saturable absorber and pulse stabilizer. The laser exhibits low timing jitter and low amplitude noise.

We demonstrate bistable operation and optical control of a specially designed distributed-Bragg-reflector laser. Optically controlled turn-on and turn-off with 1-pJ pulses at 1.5 μm and 2-pJ pulses at 1.3 μm, respectively, is demonstrated as well as all-optical flip-flop operation.