A. Mar

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. >

Actively mode-locked semiconductor lasers

Measurements of actively mode-locked semiconductor lasers are described and compared to calculations of the mode-locking process using three coupled traveling-wave rate equations for the electron and photon densities. The dependence of pulse width on the modulation current and frequency are described. A limitation to minimum achievable pulse widths in mode-locked semiconductor lasers is shown to be dynamic tuning due to gain saturation. Techniques to achieve subpicosecond pulses are described, together with ways to reduce multiple pulse outputs. The amplitude and phase noise of linear- and ring-cavity semiconductor lasers were measured and fond to be tens of dB smaller than YAG and argon lasers and limited by the noise from the microwave oscillator. High-frequency phase noise is only measurable in detuned cavities, and is below -110 dBc (1 Hz) in optimally tuned cavities. The prospects for novel ways to achieve even shorter pulses are discussed. >

Resonantly enhanced semiconductor lasers for efficient transmission of millimeter wave modulated light

External cavity semiconductor lasers with resonantly enhanced modulation response are shown to be suitable for efficient narrowband data transmission in the millimeter-wave range (35 GHz) at frequencies beyond the intrinsic modulation bandwidth of the diode. A small-signal rate equation model is presented to analyze the modulation response as well as the amplitude noise in such a resonant transmitter system. Analysis and measurements show that the relative intensity noise is also resonantly enhanced, but the signal-to-noise ratio is not degraded.<<ETX>>

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>>

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.

High speed InGaAs/InP p-i-n photodiodes fabricated on a semi-insulating substrate

High speed, mass-produced InGaAs-InP p-i-n photodiodes have been fabricated on a semi-insulating substrate. The FWHM (full width at half maximum) impulse response of a 25- mu m/sup 2/ device has been measured to be under 16 ps, entirely limited by the measurement system. The high speed of this structure was achieved by scaling the area down to 25 mu m/sup 2/ and the intrinsic layer thickness down to 0.3 mu m. Further scaling of this structure is possible, and bandwidths in excess of 200 GHz should be achievable. This structure is also useful for integration with bias tees, matching networks, and optical and electronic preamplifiers.<<ETX>>

Mode-locked multisegment resonant-optical-waveguide diode laser arrays

The first mode-locked operation of resonant optical waveguide (ROW) semiconductor laser arrays is reported. The well-behaved emission patterns of such arrays allow coupling to external cavities with efficiencies comparable to those achieved by using single-element lasers. Single- and multisegment lasers are employed to achieve active, passive, and hybrid mode-locking. The use of an arrayed gain region is effective in increasing the saturation energies of gain and absorber segments, resulting in high pulse energies. Pulses are generated that have well-suppressed secondary pulsations, with pulsewidths as short as 5.6 ps and peak powers of over 3 W in a collimated beam with a single main lobe.<<ETX>>

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.

Curved and tapered waveguide mode-locked InGaAs/AlGaAs semiconductor lasers fabricated by impurity induced disordering

InGaAdAlGaAs quantum well semiconductor diode lasers were fabricated using impurity induced disordering [I]. The active region consisted of 3 I I Q ~ G ~ ~ ~ A s quantum wells 8 nm thick separated by 10 nm GaAs barriers, between 80 nm Alo.2Gao.sAs separate confinement regions. Impurity induced disordering is well suited for fabrication of curved and tapered waveguide devices because the process is independent of crystallographic orientation, and the diffusion process smoothes out small mask irregularities. The devices were antireflection (AR) coated and coupled to an external cavity. Passive modelocking was achieved by reverse biasing a short segment to act as an integrated waveguide saturable absorber.