Feedback power penalty in 1 Gbit/s singlemode fibre transmissionwith butt coupled VCSEL source

The authors have transmitted data at 1 Gbit/s over singlemode fibre with a bit error rate (BER) of less than 10^-11 using intensity modulated butt coupled VCSELs and direct detection. The laser-fibre coupling efficiency exceeds 90% for singlemode operation and the maximum power in the fibre is 0.5 mW. The power penalty for -10 dB feedback is as low as 1.5 dB     

Continuous-wave operation of GaInNAsSb distributed feedback lasers at 1.5 /spl mu/m

GaAs-based singlemode emission at 1.5 /spl mu/m has been realised for the first time in continuous-wave operation. GaInNAsSb active-layer material and GaAsN strain-compensating barriers have been used in combination with lateral distributed feedback. Laser diodes with a threshold current of 95 mA, an external efficiency of 0.15 W/A and a maximum output power of more than 10 mW could be demonstrated. A sidemode suppression ratio better than 31 dB could be realised at a singlemode emission wavelength of 1496 nm.     

Room temperature continuous-wave operation of GaInNAs/GaAs VCSELsgrown by chemical beam epitaxy with output power exceeding 1 mW

The authors present a near 1200 nm wavelength vertical-cavity surface-emitting laser (VCSEL) the active region of which is formed by GaInNAs/GaAs quantum wells grown by chemical beam epitaxy. Room temperature continuous-wave operation has been demonstrated with a high slope efficiency of 0.23 W/A, a high output power of over 1.0 mW, and a singlemode output power of 0.34 mW. The fabricated devices with different aperture sizes show low threshold currents of 1.2-2.1 mA and a record low threshold current density of 2.6 kA/cm² in GaInNAs VCSELs     

High power, low threshold, singlemode 630 nm laser diodes

Output powers exceeding 45 mW under room temperature, continuous wave operation and threshold currents as low as 30 mA are demonstrated in singlemode AlGaInP visible laser diodes emitting at 636 nm. Singlemode operation is maintained at output powers exceeding 40 mW.<>     

High-power singlemode CW operation of 1.5 /spl mu/m-range quantum dot GaAs-based laser

Narrow ridge stripe lasers with metamorphic InAs/InGaAs quantum dots grown using molecular beam epitaxy on GaAs substrates emit in the 1.5 /spl mu/m wavelength range demonstrating a differential quantum efficiency of about 50%, singlemode operation, and maximum continuous-wave power of 220 mW limited by thermal roll-over. Absence of beam filamentation is demonstrated up to the highest power levels studied.     

Polymeric variable optical attenuator based on long range surface plasmon polaritons

Proposed is a polymeric variable optical attenuator based on long range surface plasmon polaritons (LRSPPs) along a thin metal stripe embedded in polymers. The device is operated by controlling radiation loss of the LRSPP mode resulting from the temperature gradient of the polymer cladding caused by a heater. For guiding LRSPPs and efficient coupling of singlemode fibres, gold stripes 20 nm thick, 4 /spl mu/m wide and 1 cm long are utilised. To obtain a long physical lifetime, the heater is formed on the top of the polymer cladding with a 200 nm Au film which is about ten times thicker than the thin metal waveguide. The fabricated device is characterised at a wavelength of 1.55 /spl mu/m, exhibiting high attenuation of less than 30 dB with an operating power of 100 mW. A fibre-to-fibre total insertion loss of 6.1 dB is achieved when using singlemode fibres.     

High efficiency long wavelength VCSEL on InP grown by MOCVD

High efficiency continuous-wave operation of 1.53 /spl mu/m vertical cavity surface emitting lasers (VCSELs) with buried tunnel junction grown by metal organic chemical vapour deposition (MOCVD) has been demonstrated. Devices show a high differential quantum efficiency of 46% and a singlemode power of 1 mW. Minimum threshold current and voltage are 0.45 mA and 1.3 V at room temperature, respectively for devices of 5 /spl mu/m diameter.     

Green-emitting organic vertical-cavity laser pumped by InGaN-based laser diode

An organic vertical-cavity surface-emitting laser is demonstrated, which is pumped by an InGaN-based blue laser diode. The vertical-cavity laser structure consists of a poly-N-vinylcarbazole film doped with Coumarin 540A and two Bragg reflectors made of TiO₂/SiO₂ quarter-wave thin films. By driving the pump laser diode with a pulse width of 3.5 ns, singlemode lasing was achieved at a wavelength of 540 nm for a threshold pump power of 137 mW/pulse.     

Optical particle manipulation by application-specific densely packed VCSEL arrays

Densely packed arrays of vertical-cavity surface-emitting lasers (VCSELs) are presented, serving as low-cost and small-sized laser sources in optical particle manipulation systems. A novel, self- aligned fabrication process enables both a pitch in the 20 mum range and a selective surface etch for enhanced transverse singlemode emission. Homogeneous array performance and singlemode output powers of up to 3.8 mW are observed. By inserting the arrays into an optical tweezer setup with external optics, multiple optical traps are easily created. Non-mechanical particle translation by switching between individually addressable devices as well as continuous particle deflection in a one-dimensional optical lattice are demonstrated.     

Singlemode output power enhancement of InGaAs VCSELs by reducedspatial hole burning via surface etching

Completely singlemode MBE-grown selectively oxidised InGaAs-VCSELs with aperture diameters of up to 14 μm have been fabricated using a self-aligned shallow surface etch. By choosing the growth position accordingly, a continuous variation of the aperture diameter across the wafer is achieved to optimise the surface etch to aperture diameter ratio. A record singlemode output power of 5.7 mW (30 dB SMSR) is obtained for a 5.8 μm-aperture diameter, 2.8 μm etch spot diameter device     

High-performance 1.6 μm single-epitaxy top-emitting VCSEL

The first single-epitaxy top-emitting vertical-cavity surface-emitting laser emitting in the 1.55-1.61 μm wavelength region is reported. CW operation is achieved up to 55°C with an optical power of 0.45 mW obtained at 25°C. Error free transmission by these lasers at 2.5 Gbit/s is obtained over 50 km of singlemode fibre without the need for optical amplification     

Photorefractive effect and high power transmission in LiNbO/sub 3/ channel waveguides

The photorefractive index changes in singlemode annealed proton exchanged channel waveguides is measured for guided powers of more than 100 mW at 1064 nm. Wave guidance up to 2 W is demonstrated.     

0.7 W in singlemode fibre from 1.48 μm semiconductorunstable-cavity laser with low-confinement asymmetric epilayer structure

Applied to 1.48 μm high-power unstable-cavity lasers, the concept of low modal gain is demonstrated to efficiently repel filamentation effects, enabling more than 700 mW to be coupled in a singlemode fibre from a single semiconductor laser diode     

1550 nm-band VCSEL 0.76 mW singlemode output power in 20-80/spl deg/C temperature range

Wafer-fused InGaAlAs/AlGaAs vertical cavity surface emitting lasers with InAlGaAs-based tunnel junction injection have shown record high 0.7 mW singlemode output power in the 10-80/spl deg/C temperature range. Single transverse-mode operation with 35 dB sidemode suppression and low divergence beam with 9/spl deg/ half width at half maximum has been measured on devices with 7 /spl mu/m aperture.     

InAs/GaInAs quantum dot DFB lasers emitting at 1.3 μm

Singlemode operation of 1.3 μm InAs/GaInAs quantum dot lasers has been achieved using the concept of complex coupled distributed feedback. Mode selection was realised by laterally patterned metal gratings. At room temperature the lasers show stable singlemode emission with sidemode suppression ratios of up to 55 dB, threshold currents as low as 17 mA and output powers of up to 8 mW under continuous wave operation     

High-efficiency CW thulium-sensitised holmium-doped fluoride fibre laser operating at 2.04 mu m

Laser oscillation at 2.04 mu m has been observed in a thulium-sensitised holmium doped singlemode fluorozirconate fibre. 52% slope efficiency and 250 mW output power were obtained with a pump at 0.82 mu m. Cross relaxation in thulium gives a pump quantum efficiency of 1.30.<>     

Laser emission and amplification at 1.3 mu m in neodymium-doped fluorophosphate fibres

Laser emission and amplification have been studied in the 1.3 mu m spectral region on the /sup 4/F/sub 3/2/-/sup 4/I/sub 13/2/ transition in Nd/sup 3+/-doped fluorophosphate singlemode fibres. Pumping at 800 nm yields an extracted laser power of 10 mW at 1.323 mu m. A gain higher than 3 dB was obtained at the same wavelength in the amplifier experiment.<>     

Wavelength and intensity stabilisation of 980 nm diode laserscoupled to fibre Bragg gratings

The wavelength and intensity of 980 nm diode lasers are stabilised by coupling the lasers to low-reflectivity (<5%) fibre Bragg gratings. Power of up to 100 mW from the singlemode fibre has been obtained. The increased stability of these permanently mounted devices may result in improved performance of erbium-doped fibre amplifiers     

S-band Brillouin erbium fibre laser

A multi-wavelength Brillouin erbium fibre laser, which operates in short wavelength band (S-band), is proposed and demonstrated. The system employs both linear gain and nonlinear gain from a 20 m S-band erbium-doped fibre and a 500 m singlemode fibre, respectively, to generate an optical wavelength comb with spacing of approximately 0.084 nm. Two 80/20 couplers were used in the system as an internal feedback of generated Stokes signal to produce cascaded Brillouin Stokes for multiwavelength operation. A stable output laser comb of up to seven lines was obtained with a Brillouin pump of 3.5 mW and a 980 nm pump of 200 mW.     

DFB and DBR lasers emitting at 980 nm

The performance of DFB and DBR ridge waveguide lasers operating at 980 nm is reported. The DBR devices used a single growth step and gave singlemode output powers as high as 30 mW. The DFB devices used a two-step growth process in which the lower cladding and active regions were grown fast, the gratings were etched and then the upper cladding and p-contact layers were regrown on top of the grating. The DFB devices gave output powers as high as 75 mW.<>