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We demonstrate novel electrically pumped 1300 nm and 1550 nm VCSELs with two InP/air-gap DBRs. The activeregions comprise conventional InGaAsP multiple quantum wells. A tunnel junction is placed between the active regionand top DBR to convert electrons into holes, thus minimizing the use of p-type material in the structure to reduce thefree-carrier loss and achieve current confinement. The whole structure was grown in a single growth run by lowpressure MOCVD. For both 1300 and 1550 nm emission wavelengths, air-gap DBR VCSELs exhibit room-temperature, CW threshold current density as low as 1.1 kA/cm 2 , differential quantum efficiency greater than 30%, andCW operation up to 85°C. The single-mode output power was 1.6 mW from a 1300 nm VCSEL with a 6.3 µ maperture; and 1.1 mW from a 1550 nm VCSEL with a 5.7 µ m aperture under room temperature CW operationKeywords: long wavelength VCSELs, vertical-cavity surface-emitting laser, InP/Air-gap DBRs, tunnel junctions,distributed Bragg reflector, quantum well lasers, semiconductor lasers.

A simple model is used to design and optimize masks that when etched onto the aperture of a normally multi-mode gain guided vertical-cavity surface-emitting laser, VCSEL, cause the device to lase in a single transverse mode. After etching, Gaussian beam profiles for the LP01 mode are achieved over the entire operating current range with greater than 16 dB modal suppression. To date single mode emission at 2 mW has been achieved with pinning of the nearfield width. The modelling shows that the etching introduces a spatial filter on the higher order modes. The power in the fundamental mode remains constant before and after etching.

A study of the gain-switching process in GaInN MQW laser diodes is reported. Single peak gain-switched optical pulses with pulse widths less than or equal to 40 ps and optical powers equal to 100 mW are observed when electrical pulses with duration of 800 ps are applied. Sub-nanosecond optical pulses with peak powers in excess of 450 mW are also obtained and degradation mechanisms are analyzed. The transient response characteristics of the laser diodes are studied in both the time and spectral domains.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper reviews novel techniques which are used to modify the properties of the optical beam generated by vertical cavity surface emitting laser diodes. The main emphasis within the paper concerns the use of etches applied to the device surface either adjacent to or across its optical aperture. Such etches can be used to modify facet reflectivities sufficiently to pin the optical mode precisely and reduce the onset of higher order modes. In addition, single polarization operation is achieved by using deeper etches placed outside the light emitting region. Using this technique, previously multimode components may be transformed to single mode components with precisely fixed polarization states. The effect of these etches on other lasing properties such as spectral performance and power efficiency is also discussed.

As the modulation bandwidth of a travelling wave modulator is increased, thevelocities of the microwave and the lightwave need to be taken into consider-ation. Velocity mismatch of 20% or greater can occur in a ITT-V modulatorand this will result in a bandwidth of approximately 22 GHz-cm or less foran electrical loss of 1 dB/GHz1/2-cm. To improve the bandwidth of the mod-ulator to greater than 40 GHz, velocity mismatch would have to be reducedto within 10%. A new velocity matched ITT-V modulator will be prsented. Background and Structure Two structures, the PIN microstrip structure and the NIN coplanar strip structure have been studied and both exibited velocity mismatch. In the mi-crostrip structure, the microwave velocity is dispersive and travelling slower than the optical wave, whereas in the coplanar strip case, the microwavetravels faster than the optical wave [1]. It seems reasonable that a hybridmicrostrip-coplanar strip structure could be found where the velocities arematched. This new structure ,the planar microstrip (PMS), demonstrated