Low threshold voltage vertical-cavity lasersfabricated by selective oxidation

Abstract

inserted between them to suppress spontaneous emission light [5, 6]. A stable tilt splice of 25° with a loss of less than 0.2dB was attained between the PDF and the high-NA silica fibre by using the V -groove connection technique. Reflectivity of less than -60dB was achieved using the tilted V -groove connection. The signal source was a DFB laser operating at 1302nm and its output power was 6.5dBm. 40ch carriers ranging from 91.25 to 403.25MHz directly modulated the DFB · laser with a modulation depth of 5.6%/ch. The DFB laser output was amplified by the PDFA and attenuated with a variable optical attenuator. CNR and distortion characteristics were measured for three carrier frequencies, 91.25, 211.25, and 403.25 MHz. Fig. 3 shows the CNR at 403.25MHz as a function of loss budget with and without a PDFA.The CNR was the same in the measured three channels. The loss budget improvement for 52dB CNR was IOdB. The NF was 9.8dB as estimated from the CNR degradation. We believe that the NF improvement from previous reports is due to selecting low loss PDF and that further NF improvement can be expected by suppressing PDF scattering.

Proton implanted singlemode holey vertical-cavity surface-emitting lasers

“…This structure has several advantages over oxide confined devices. First, implant devices are inherently singlemode at threshold, and only lase in a few higher-order transverse modes at higher current, whereas oxide devices with similar aperture sizes are strongly index-guided from threshold to saturation [10]. Because of this, the loss to higher-order modes that is introduced by the holey structure causes the threshold current to increase in oxide-confined devices.…”

Selectively oxidised vertical cavity surface emittinglaserswith 50% power conversion efficiency

“…Such gainguided devices have modal properties that are strongly dependent on thermal lensing [9][10][11], and they do not scale well to smaller diameters because of optical diffraction losses [12,13]. The incorporation of oxides for index guiding circumvents these problems as well as providing current confinement [4,5] and has led to a four-fold improvement in the power conversion efficiency of VCSEL diodes at low current levels, reaching 50% for the first time.…”

“…The differential quantum efficiency of 78% just above threshold is largely due to the aggressive output coupler design. This excellent optical performance combines with excellent electrical performance originating from the tight current confinement and absence of implant induced damage afforded by selective lateral oxidation [4,5] and the low lateral and vertical resistance of uni-parabolic mirror grading [14,15] to yield a maximum power conversion efficiency of 50.2%. This is especially noteworthy in that it occurs at less than 2mA of operating current.…”

“…Index-guiding and current aperture layers were formed by selective lateral oxidation as previously described by Choquette et a/. [4,5]. Following the wet thermal oxidation, backside and annular topside contacts were deposited and alloyed.…”

Vertical cavity lasers on p -doped substrates

“…Within each mirror period, the minimum aluminum mole fraction was 0.16 and the maximum varied between 0.94 and 0.97 for all of the mirror periods, except for the p-type mirror period next to the cavity, which incorporated Alo. 98 Gav 02 As to selectively oxidise a confinement layer at this position [6]. Note that the confinement layer defines a current constriction which is just above the cavity for the n-substrate samples and just below the cavity for the p-substrate sample.…”