Dennis J. Derickson

Short pulse generation using multisegment mode-locked semiconductor lasers

Mode-locked semiconductor lasers which incorporate multiple contacting segments are found to give improved performance over single-segment designs. The functions of gain, saturable absorption, gain modulation, repetition rate tuning, wavelength tuning, and electrical pulse generation can be integrated on a single semiconductor chip. The optimization of the performance of mode-locked lasers in terms of material parameters, waveguiding parameters, electrical parasitics, and segment length is discussed experimentally and theoretically. >

Comparison of timing jitter in external and monolithic cavity mode‐locked semiconductor lasers

A comprehensive timing jitter comparison is made for mode‐locked semiconductor lasers using active, passive, and hybrid mode‐locking techniques in both external and monolithic cavity configurations. Active mode locking gives the lowest residual rms timing jitter of 65 fs (150 Hz‐50 MHz), followed by the hybrid and passive mode‐locking techniques. It is found that monolithic cavity devices with all active waveguides have higher timing jitter levels than the comparable external cavity case.

ULTRAFAST DYNAMICS IN FIELD-ENHANCED SATURABLE ABSORBERS

Absorption recovery dynamics of GaAs/AlGaAs field‐enhanced waveguide saturable absorbers are studied by pump‐probe differential transmission measurements. We compare the response of bulk and single quantum well absorbers at different reverse bias levels and pump powers, and find an ultrafast transient in the response, followed by a slower rise before the final recovery. The absorption fully recovers after a few picoseconds, which is an important result for mode‐locked lasers.

Suppression of multiple pulse formation in external-cavity mode-locked semiconductor lasers using intrawaveguide saturable absorbers

Imperfect antireflection coatings in external-cavity mode-locked semiconductor lasers can cause multiple output pulse generation. The incorporation of an intrawaveguide saturable absorber segment into the laser suppresses this problem. Single pulse outputs of less than 2.8 ps and 0.7 pJ of energy are obtained using such devices with both quantum well and bulk active regions.<<ETX>>

Analysis of laser pulse chirping in mode-locked vertical cavity surface-emitting lasers

Mode-locked vertical cavity lasers have a large cross-sectional area and consequently a large saturation energy and large peak powers. The authors analyze excess optical bandwidth generation in these lasers and find that self-phase modulation due to optical pumping and gain saturation is the dominant factor in inducing laser pulse chirping. The large magnitude of the chirp makes intracavity prism-pair compensation difficult. Adjustment of the cavity length has a major impact on the pulse chirping, as observed experimentally. Proper adjustment can result in a large linear frequency chirp which can be compensated using external pulse compression techniques. >

Microwave and millimeter wave signal generation using mode-locked semiconductor lasers with intra-waveguide saturable absorbers

The authors consider electrical and optical signal generation techniques using passively and hybridly mode-locked semiconductor lasers with intra-waveguide saturable absorbers. Microwave and millimeter-wave signals can be generated using mode-locked semiconductor lasers with the intra-waveguide saturable absorbers. Monolithic and external cavity devices optimized for electrical and optical signal generation are discussed along with measurements of amplitude noise, phase noise, output power, and repetition rate tunability.<<ETX>>

Self-Mode-Locking of a Semiconductor Laser Using Positive Feedback

A new mode‐locking technique, self‐mode‐locking, is described which uses the detected optical pulses from the mode‐locked laser as the active driving source. This technique forms narrow‐width mode‐locked optical pulses at low repetition rates without the use of a microwave synthesizer.

Actively mode-locked external-cavity semiconductor lasers with transform-limited single-pulse output.

We describe the use of split-contact semiconductor laser diodes to suppress multiple-pulsing phenomena in actively mode-locked external-cavity lasers. The laser-diode length is critical for the elimination of multiple-pulse output. With a grating installed in the external cavity, 11.5-ps pulses are generated that have a time–bandwidth product of only 0.30, an important property for use in soliton transmission systems. By using a broadband mirror in place of the grating, nearly transform-limited single pulses of 1.4-ps duration are generated at a 3-GHz repetition rate.

High speed photodetectors

High speed photodetectors are required for use in high speed optical interconnects. Recent results on high speed photodetectors are reviewed, and devices with important implications for future high speed photodetector operation are considered.

Monolithic mode locked laser arrays in optical computing

Modelocked semiconductor lasers are a source of subpicosecond pulses at high repetition rates with very low phase noise. This makes them ideal sources for clock/strobe signals for OEICs and optical computing, for high data rate input devices and for use in optical digital-to-analog converters. These applications will be described in this paper, together with an outline on the state of the art in modelocked semiconductor lasers.