A. Valster

DIODE-PUMPED CR:LISAF ALL-SOLID-STATE FEMTOSECOND OSCILLATOR AND REGENERATIVE AMPLIFIER

An all-solid-state tunable diode-pumped Cr3+:LiSrAlF 6 (Cr:LiSAF) regenerative amplifier, seeded by a tunable diode-pumped Cr:LiSAF femtosecond oscillator, has been demonstrated for the first time to our knowledge. The oscillator was tunable over 75 nm and generated pulses as short as 24 fs. As much as 70 mW average output power was obtained with pulses of 40-fs duration. The amplifier produced recompressed pulses of less than 200-fs duration with energies exceeding 1 μJ at a repetition rate as high as 25 kHz.

Determination of the GaInP/AlGaInP band offset

Low‐temperature photoluminescence excitation spectra of disordered Ga0.5In0.5P/Al0.3Ga0.2In0.5P quantum wells lattice matched to (311)B GaAs substrates have been measured for the first time. Transition energies calculated with a k⋅p approach agree with experiment within 3 MeV, over the entire range of quantum well thicknesses (Lz=11–109 A). A conduction‐band discontinuity of 0.65±0.05 is derived.

Kink power in weakly index guided semiconductor lasers

A periodic dependence of kink power on laser length is observed and explained. Weakly index guided high power stripe lasers in the AlGaAs, InGaAlP, and InGaAs–AlGaAs material systems are studied and oscillation periods of 100–350 μm are found. Relative kink power differences exceeding a factor of 4 are observed. Facet coatings lead to differences in the oscillation amplitude but not in the oscillation period. The observations indicate that phase‐locked fundamental and first‐order modes exist at certain preferred laser lengths. This general model fully explains the oscillatory behavior of the kink power and the correlated changes in lateral far field distributions at the front and rear mirrors. It is concluded that the optimum diffraction limited power output can be obtained by choosing the proper laser length.

High quality AlxGa1−x−yInyP alloys grown by MOVPE on (311) B GaAs substrates

Abstract High quality Ga 0.5 In 0.5 P and Al 0.25 Ga 0.25 In 0.25 P bulk layers as well as Ga 0.5 In 0.5 P/Al 0.3 Ga 0.2 In 0.5 P multiple quantum well (QW) structures have been grown by LP-MOVPE on exactly (100) and (311)B oriented GaAs substrates. The low temperature photoluminescence spectra of the AlGaInP epitaxial layers grown on (311)B GaAs substrates show a significant reduction of the linewidth at half maximum and a peak energy increase by 100–150 meV due to disordered arrangement on the group III sublattice. QWs are characterized by high resolution TEM and photoluminescence excitation measurements. For the first time, well defined electron-heavy-hole and electron-light-hole transitions have been demonstrated. The observed transitions can be fitted within 3 meV] for all wells by means of the k · p theory resulting in accurate determination of the confinement levels as a function of layer thickness. CW operation of a GaInP/AlGaInP double-heterostructure laser grown on (311)B GaAs is reported with an emission wavelength at room temperature of 651 nm which is 24 nm shorter than the 675 nm wavelength of a similar laser grown on (100) GaAs without any change in the threshold current density.

Effect of strain on the threshold current of GaInP/AlGaInP quantum well lasers emitting at 633 nm

For the first time the performance of visible lasers operating at 633 nm is reported as function of the amount of applied strain. Varying the strain between /spl delta/a/a = -1 % and /spl delta/a/a = + 1 % two minima in threshold current density have been found and are explained.

Ultralow-pump-threshold, femtosecond Cr 3+ :LiSrAlF 6 laser pumped by a single narrow-stripe AlGaInP laser diode

We report what we believe to be the first demonstration of a Kerr-lens mode-locked Cr(3+):LiSrAlF(6)laser that is pumped by a single narrow-stripe AlGaInP laser diode with a diffraction-limited output beam. A novel low-loss three-mirror laser cavity design is described in which strong, localized Kerr lensing was exploited such that 75-fs-duration pulses were obtained for only 36mW of incident pump power. This pump power was maintained for 18h by just three AA batteries as the electrical power source. We have shown that mode locking can be sustained for pump powers as low as 22mW.

Investigation of the temperature dependence of the threshold current density of GaInP/AlGaInP double‐heterostructure lasers

The temperature dependence of the threshold current density of GaInP/AlGaInP double‐heterostructure lasers is investigated over a wide temperature range. Using a theoretical calculation of the temperature dependence of the recombination rate in the active layer, the experimentally obtained threshold current density is separated into a component due to recombination in the active layer and an additional component responsible for an increased temperature dependence at higher temperature. For the additional component, a thermal activation energy of 0.27 eV is found. It is argued that this value is too low for a simple explanation based on carrier leakage.

Argon-ion-pumped and diode-pumped all-solid-state femtosecond Cr:LiSrAlF(6) regenerative amplifiers.

A tunable femtosecond solid-state amplifier system that uses only 3 W of 488-nm argon-ion pump power has been demonstrated to deliver microjoule pulses at repetition rates up to 20 kHz, with a maximum pulse energy of 14 mu;J obtained at 5 kHz. An all-solid-state, tunable, diode-pumped Cr:LiSrAlF(6) regenerative amplifier has been demonstrated, for the first time to our knowledge, that amplifies femtosecond pulses to energies exceeding 1 mu;mJ at up to a 16-kHz repetition rate.

Strain-overcompensated GaInP-AlGaInP quantum-well laser structures for improved reliability at high-output powers

Strain overcompensated multiple quantum well laser structures have been analyzed theoretically as well as experimentally for the first time. Strain overcompensation reduces the bandgap shrinkage which normally takes place at the facets due to compressive strain relaxation. This results in a lower temperature rise of the lasing spot leading to a remarkable improvement of the reliability of high power laser diodes.

Development of a red VCSEL-to-plastic fiber module for use in parallel optical data links

This paper presents results that have emerged from the European funded ESPRIT Project, Bright Red Surface Emitting Lasers (BREDSELS-23455). The projects main objective has been to develop arrays of Vertical Cavity Surface Emitting Lasers (VCSELs) emitting in the region of 650 nm. These VCSEL arrays, suitably coupled to plastic fiber ribbon, are potentially ideal sources for high-speed plastic optical fiber networks. Linear 1 X 8 VCSEL arrays have been fabricated from wafers grown in multi-wafer MOVPE reactors. Individual VCSELs are shown to generate a peak room temperature power of 2 mW at 674 nm and are capable of operating continuous wave to a temperature of 60 degrees Celsius. The use of selective oxidation in the fabrication process is found to be essential in terms of providing effective heat sinking to the active region, while free carrier absorption is found to be a significant loss mechanism. A detailed description of the device results including modal behavior is presented along with the initial results from the plastic fiber ribbon module.