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Indium phosphide-based quantu m dash mode-locked lasers designed for optical telecomunications applications are designed. These generate picosecond pulses at different repetition frequencies with low timing jitter and can be used to achieve all-optical clock recovery.

A thin-disk Yb:YAG laser is made from a Q-switched oscillator and a multipass amplifier delivering pulses of 48 mJ at 1030 nm. A novel method is described for studying the effective Yb:YAG upper state lifetime and it is used for determining gain and stored energy in the active medium and also understand the limiting factors for energy scaling of thin-disk lasers.

A strategy is described for designing a four-wavelength quantum cascade (QC) laser source with different emission wavelengths is operated by using a single current channel. The four-wavelength QC laser source has included two different heterogeneous cascade QC lasers and the threshold current densities of QC lasers are less than a factor of 2 for cavity lengths 3.0 and 3.5 mm, making the four-wavelength QC laser source convenient to use with a single current channel.

We describe a widely tunable coupled-cavity semiconductor laser with a nearly continuous tuning capability of ~100 nm. A below threshold model for coupled-cavity devices using a transfer matrix approach that takes into account the tilt of the facets forming the gap between the coupled sections was developed and is presented. Nonlinear fits of the below-threshold spectra to the model were used to extract device parameters. These fits and parameters were then used to understand the operation of the devices and the direction to take to improve the performance of the devices. It is observed that for facet angles [greater than or equal to] 7[degrees], a two-section coupled-cavity device works like an injection-locked laser, while for angles [less than or equal to] 4[degrees], the sections work as a truly-coupled system. OCIS codes: 140.0140, 140.3325, 140.3570, 140.3600, 140.5960.

Concerns about the health effects of nitrogen dioxide (N[O.sub.2]) and its role in forming deleterious atmospheric species have made it desirable to have low-cost, sensitive ambient measurements of N[O.sub.2]. We have developed a continuous-wave laser-diode laser-induced fluorescence (LIF) system for N[O.sub.2] that operates at ambient pressure, thereby eliminating the need for an expensive pumping system. The current prototype system has achieved sensitivity several orders of magnitude beyond previous efforts at ambient pressure (limit of detection of 2 ppb, 60 s averaging time). Ambient measurements of N[O.sub.2] were made in Portland, Oregon using both the standard N[O.sub.2] chemiluminescence method and the LIF instrument and showed good agreement ([r.sup.2] = 0.92). OCIS codes: 120.2440, 010.1120, 140.2020, 300.2530, 330.6100.

A large current- and temperature-induced beam-steering effect, observed in the far-field distribution of InP-based quantum-cascade lasers emitting around 7.8-[micro]m wavelength operated in pulsed mode is reported. The time-resolved spectroscopy of the lasing spectrum for the laser provides insight into the beam steering effect which is linked to changes in the lateral mode distribution.

A detailed study of an array-format 1.055[micro]m microchip semiconductor disk laser that utilizes a microlens-patterned diamond both as an array of stabilizing output coupling mirrors and a heatspreader is reported. The results from the thermal study confirmed the thermal management capabilities and power scalability of the microlensed diamond configuration.

The design of a broad tunable high-performance quantum-cascade (QC) laser source for broad-band applications and broad-band tuning at room temperature in an external cavity (EC) setup is reported. The usability of the QC laser chip for broad-band tuning is proved by antireflection coating on the front facet with a residual reflectivity and used in EC setup operated at room temperature.

The development of a fiber coupled integrated external cavity laser (micro-ECL) system with a broad tuning range of 152 nm around a center wavelength of 2.1 [micro]m, based on a (AlGaIn)(AsSb) quantum well diode laser, is described. The maximum output power of the fiber coupled microECL system is found to vary only moderately between 22 and 10 mW across the tuning range.

Theoretical studies based on density-matrix equations, including the effects of carrier density pulsations, carrier heating, spectral hole burning, and carrier diffusion are used to study the nonlinear gain in semiconductor ring lasers. The results showed that carrier diffusion have strong effects on both the amplitude and heat frequency dependency of the nonlinear susceptibilities.

A new model is used for the calculation of the output characteristics of a fiber Bragg grating (FBG)-stabilized pump-laser module depending on the effective feedback from the grating. Findings reveal the capability of the proposed model in accurately simulating the properties of the wavelength-stabilized pump-laser module.

To maintain the same beam quality as that of a single emitter and to be close to diffraction limit, we have combined a phase corrected array, emitting at [lambda] = 975 nm, cohe rently using the Talbot effect. First, to improve the beam quality of the array, a phase correcting system was added. The FWHM divergences of the array (which is approximately the same as that of the single emitter since the emitters within the array are not optically coupled to each other) were reduced from 34[degrees] to 0.17[degrees] in the fast axis and from 3.5[degrees] to 0.7[degrees] in the slow axis at 6A. Then, to be close to the diffraction limit, we have combined this corrected array coherently using the Talbot effect. We have obtained a quasi-monolobe slow axis far field profile for the in-phase mode with a central peak divergence of only 0.27[degrees] at 1.5 A, 315 mW under cw operation, and of only 0.20[degrees] at 2.5 A, 787 mW under pulsed operation. To our knowledge, this is the first demonstration of coherent coupling of a corrected tapered laser diode array in an external Talbot cavity. OCIS codes: 140.2010, 140.0140, 140.5960.

The damaged region of a semiconductor laser diode that failed in a vacuum environment is analyzed. The studies have shown that failure proceeded by pyrolysis of adsorbed hydrocarbons on the antireflective (AR) coating has contributed to carbothermal reduction of the AR coating.

The article examines the polarization-resolved spatial emission and turn-on dynamics of oxide-confined vertical-cavity surface-emitting lasers (VCSELs) with an integrated surface-relief grating. Findings reveal guaranteed stable turn-on on a single polarization due to the high dichroism of the grating.

A method for increasing the differential slope efficiency of semiconductor gain-lever lasers via modification of the cavity geometry is presented. Results suggest the achievement of high slope efficiency, low nonlinearity, large modulation bandwidth and large output power.

The pulse dynamic and stability harmonically mode-locked semiconductor lasers are examined. Results suggest the capability of dynamic gain saturation is stabilizing harmonic mode-locking.

The article presents a SPICE-like approach for solving the detailed current and voltage distributions in vertical-cavity surface-emitting lasers (VCSELs). The mode changes are a result of hole burning due to anisotropy of the resistivity of the p-distributed Bragg reflector (p-DBR) mirror.

Numerical simulations were used for examining the impact of charge carrier and triplet-exciton absorption on the threshold current density of an organic double-heterostructure (DH) laser diode structure. Findings revealed no significant reduction in polaron absorption due to an increase in charge carrier mobility in the transport layers.

The dynamic characteristics of semiconductor lasers subjected to pseudorandom digital modulation at gigabit rates are investigated. The findings have shown that the bit pattern is the major contributor to the turn-on jitter (TOJ) when the setting time of the relaxation oscillation is longer than the bit slot.

The continuous tuning range of an external-cavity diode laser can be extended by making small corrections to the external-cavity length through an electronic feedback loop so that the cavity resonance condition is maintained as the laser wavelength is tuned. By maintaining the cavity resonance condition as the laser is tuned, the mode hops that typically limit the continuous tuning range of the external-cavity diode laser are eliminated. We present the design of a simple externalcavity diode laser based on the Littman-Metcalf external-cavity configuration that has a measured continuous tuning range of i GHz without an electronic feedback loop. To include the electronic feedback loop, a small sinusoidal signal is added to the drive current of the laser diode creating a small oscillation of the laser power. By comparing the phase of the modulated optical power with the phase of the sinusoidal drive signal using a lock-in amplifier, an error signal is created and used in an electronic feedback loop to control the external-cavity length. With electronic feedback, we find that the continuous tuning range can be extended to over 65 GHz. This occurs because the electronic feedback maintains the cavity resonance condition as the laser is tuned. An experimental demonstration of this extended tuning range is presented in which the external-cavity diode laser is tuned through an absorption feature of diatomic oxygen near 760 nm. OCIS codes: 140.3600, 140.5960, 280.3420, 300.6260.

We report the operation of an optical in-well-pumped vertical-external-cavity surface-emitting laser. The laser delivers 1 W at 855 nm and is pumped with a cost-effective fiber-coupled laser diode emitting at 806 nm. The laser modal gain is examined and ways of optimizing the system are investigated and discussed. OCIS codes: 140.3480, 140.5960, 140.5560, 230.5590, 250.7260.

The adequacy of commercial quasi-continuous high-power laser diode arrays (HPLDAs) as pump sources for spaceborne lasers has been assessed by endurance tests up to 3 x [10.sup.9] shots under various stress conditions, vacuum operation up to 0.36 x [10.sup.9] shots, and proton radiation tests. Observations of the evolution of the electro-optic parameters and of the near-field patterns of the HPLDAs during endurance tests have revealed that some diode bars could reach the required lifetime of a multibillion shots, suggesting how to build long lifetime HPLDAs by proper selection of the diode bars. The robustness of the HPLDAs against the proton environment experienced in a typical low Earth orbit has been checked. Finally, high-power laser diode arrays have been operated under vacuum, showing a behavior similar to that of HPLDAs operating in atmospheric conditions. OCIS codes: 140.2010, 140.2020, 140.5560, 350.6090, 350.4800.

GaInAsSb/GaA1AsSb/GaSb distributed-feedback (DFB) laser diodes based on a type I active region were fabricated by molecular beam epitaxy at the Centre d'Electronique et de Micro-Optoelectronique de Montpellier (CEM2). The DFB processing was done by Nanoplus Nanosystems and Technologies GmbH. The devices work in the continuous-wave regime above room temperature around an emission wavelength of 2.3 [micro]m with a side-mode suppression ratio greater than 25 dB and as great as 10 mW of output power. The laser devices are fully characterized in terms of optical and electrical properties. Their tuning properties made them adaptable to tunable diode laser absorption spectroscopy because they exhibit more than 220 GHz of continuous tuning by temperature or current. The direct absorption of C[H.sub.4] is demonstrated to be possible with high spectral selectivity. OCIS codes: 140.3070, 120.0280.

The power spectrum of the laser intensity is studied when optical feedback in a laser diode is used as a sensing configuration for dynamic light-scattering experiments. We present a theory that relates the power spectrum obtained from standard dynamic light-scattering theory to the intensity power spectrum of the laser. This theory provides a concise description of this sensing technique, also known as self-mixing interferometry, when it is applied to Doppler shift and line-broadening measurements of the backscattered field. OCIS codes: 120.3180, 290.3700, 290.0290, 140.2020.

We report substantially improved performance of high-power quantum cascade lasers (QCLs) by using epitaxial-side-down mounting that provides superior heat dissipation properties. We used aluminum nitride as the heatsink material and gold-tin eutectic solder. We have obtained continuous wave power output of 450 mW at 20[degrees]C from mid-IR QCLs. The improved thermal management achieved with epitaxial-side-down mounting combined with a highly manufacturable and scalable assembly process should permit incorporation of mid-IR QCLs in reliable instrumentation. continuous wave operation | room temperature operation | high-power lasers | mid-IR semiconductor lasers

A diode-pumped passively Q-switched Nd:YV[O.sub.4] green laser with a periodically poled KTP and [Cr.sup.4+]:YAG saturable absorber is realized. The dependences of pulse repetition rate, pulse energy, pulse width, and peak power on incident pump power are measured for the generated green-light pulses. A rate-equation model is introduced to theoretically analyze the results obtained in the experiment, in which the spatial distribution of the intracavity photon density is taken into account. The numerical solutions of the rate equations agree with the experimental results. OCIS codes: 140.3540, 140.3530, 140.3580, 140.3480, 140.3430.

A comprehensive theoretical description of passive mode-locking in external-cavity mode-locked semiconductor lasers based on a fully distributed time-domain approach is developed. The model accounts for the dispersion of both gain and refractive index, nonlinear gain saturation from ultrafast processes, self-phase modulation, and spontaneous emission noise.

Detailed numerical analyses based on the conventional single-mode rate equations and a carrier heating model were performed to study the nonlinear behavior of a directly modulated 1.55 mum distributed feedback laser diode. The calculated results show the significant impact of band gap shrinkage on simulated results and also show that the carrier heating model is a self-consistent model that naturally describes the gain suppression phenomena in directly modulated laser diodes.

Mechanism causing sudden failure of InGaAs/GaAs strained-layer quantum-well lasers (LD) is analyzed by monitoring an optical beam-induced current (OBIC). The OBIC technique being nondestructive, highly sensitive and having a high-spatial resolution is extensively used in degradation analyses of optoelectronic devices.