Two-step laterally tapered spot-size converter 1.55-/spl mu/m DFB laser diode having a high slope efficiency

We demonstrate a two-step lateral tapered 1.55-/spl mu/m spot-size converter distributed feedback laser diode (SSC DFB LD) having slope efficiencies as high as 0.457 and 0.319 mW/mA measured at 25 /spl deg/C and 85 /spl deg/C, respectively. The SSC DFB LD fabricated by using a nonselective grating process has a double core waveguide structure including a planar buried heterostructure type active waveguide and a ridge type passive waveguide. The fabricated SSC DFB LD operates at 1.553-/spl mu/m wavelength and shows a far-field pattern in horizontal and vertical directions of 7.3/spl deg/ and 11.6/spl deg/, respectively.     

A two-step laterally tapered 1.55-/spl mu/m SSC DFB laser fabricated by using a nonselective grating process

We demonstrate a two-step laterally tapered 1.55-/spl mu/m spot size converter distributed feedback laser diode (SSC DFB LD) having a planar buried heterostructure-type active waveguide and a ridge-type passive waveguide fabricated by using a nonselective grating process. Unlike conventional SSC DFB LDs, where a selective grating is employed, this SSC DFB LD employed a nonselective grating over the entire device region in order to make its fabrication much simpler than that of the conventional SSC DFB LDs. The two-step laterally tapered SSC is effective in removing an unwanted wavelength peak originating from the SSC section having a multiquantum well and a grating under it. The fabricated SSC DFB LD operates at 1.553-/spl mu/m wavelength and shows a far field pattern in horizontal and vertical directions of 13.4/spl deg/ and 19.5/spl deg/, respectively.     

Low-cost 1.55-/spl mu/m InGaAsP-InP spot size converted (SSC) laser with conventional active layers

We report the realization of a low cost 1.55-/spl mu/m spot size converted (SSC) laser using conventional SCH-MQW active layers. The laser consists of a rectangular gain section, a linear taper and a passive waveguide. The lateral taper and the passive waveguide are fabricated on the same lower SCH layer, using conventional photolithography and RIE (reactive ion etching). The device exhibits low beam divergence of 6.6/spl deg//spl times/10.9/spl deg/ and -2.2-dB coupling loss with a cleaved single-mode fiber. The 1-dB alignment tolerance is /spl plusmn/2.15 /spl mu/m in vertical direction and /spl plusmn/2.3 /spl mu/m in lateral direction, respectively.     

1 W fibre coupled power InGaAsP/InP 14xx pump laser for Raman amplification

A 1 W record singlemode fibre coupled output power using 1460 nm InGaAsP/InP non-tapered buried ridge lasers has been demonstrated. The impact of the bandgap of the passive quaternary waveguide on internal loss was investigated. Optimised design allows internal losses as low as 3.3 cm/sup -1/, external efficiency of 0.46 W/A for a 3 mm-long laser and symmetrical (12/spl deg//spl times/12/spl deg/) far-field pattern.     

Spot-size converter using vertical ridge taper for low fibre-coupling loss in 2.5%-/spl Delta/ silica waveguides

A novel spot-size converter based on a vertical ridge waveguide taper for super-high-/spl Delta/ silica waveguides is demonstrated. This structure can be formed with a simple fabrication process. The coupling loss between a singlemode fibre and a 2.5%-/spl Delta/ silica waveguide was reduced to 0.31 dB/point compared to 2.7 dB/point for conventional straight waveguides.     

Hybrid-integrated external-cavity laser without temperature-dependent mode hopping

We propose and demonstrate an integrated external-cavity laser (ECL) with a novel configuration designed to suppress temperature-dependent mode hopping. The laser cavity is composed of a spot-size converter integrated laser diode (SS-LD), a UV-written grating, and silicone-filled grooves on a planar lightwave circuit (PLC). The silicone is used to compensate for the difference between the temperature coefficients of the SS-LD and the silica waveguides. We calculate theoretically the temperature interval of the mode hopping in the ECL to optimize the length of the silicone-filled grooves. We fabricated test and practical lasers with the proposed configuration using PLC hybrid-integration technologies. With the test laser, we confirmed stable single-mode oscillation and a large increase in the mode-hopping temperature interval for both static and dynamic operation. We obtained a low threshold of 15 mA, an optical power of 1.0 mW at 25/spl deg/C, and an injection current of 60 mA. In the practical laser, which we additionally integrated with a front monitor photodiode, we realized auto power control with mode-hopping-free operation from 18/spl deg/C to 56/spl deg/C. These results indicate the good performance levels of our proposed laser.     

Passively aligned hybrid WDM module integrated with spot-sizeconverter integrated laser diode and waveguide photodiode on PLCplatform for fibre-to-the-home

A low cost and high performance hybrid WDM module assembled by passive alignment has been developed for FTTH systems. High coupling efficiency of a spot-size converter integrated laser diode to a PLC waveguide, which facilitates mass production of the module, is achieved. A minimum optical received power of -37 dBm for a 50 Mbit/s burst signal is also achieved     

Ridge laser with spot-size converter in a single epitaxial step forhigh coupling efficiency to single-mode fibers

We report on a 1.55-μm InGaAsP MQW laser diode with an integrated spot-size converter fabricated in a single epitaxial step using conventional photolithography. The laser structure uses a conventional ridge guide for the active layers and a second larger ridge for the passive waveguide. Low-beam divergence of typically 9°×9° results in about 3-dB coupling losses, with a cleaved optical fiber     

1.55 micrometer ridge DFB laser integrated with a buried-ridge-stripe dual-core spot-size converter by quantum-well intermixing

A ridge distributed feedback laser monolithically integrated with a buried-ridge-stripe spot-size converter operating at 1.55 micrometre wavelength was successfully fabricated by means of low-energy ion implantation quantum-well intermixing and dual-core technologies. The passive waveguide was optically combined with a laterally exponentially tapered active core to control the mode size. The devices emit in a single transverse and single longitudinal mode with a sidemode suppression ratio of 38.0 dB. The threshold current was 25 mA. The beam divergence angles in the horizontal and vertical directions were as small as 8.0 degree X 12.6 degree, respectively, resulting in 3.0-dB coupling loss with a cleaved single-mode optical fiber.     

Room-temperature 2.81-/spl mu/m continuous-wave operation of GaInAsSb-AlGaAsSb laser

GaInAsSb-AlGaAsSb multiple quantum-well (QW) lasers with an emission wavelength of 2.81 /spl mu/m are reported. The ridge waveguide lasers with highly strained QWs show continuous-wave laser emission up to 25/spl deg/C; in pulsed mode, the lasers operate up to 60/spl deg/C. For pulsed operation, a threshold current density of 360 A/cm/sup 2/ is found for devices with 30-/spl mu/m stripe width and 2-mm cavity length at room temperature. A low threshold current density at infinite length of 248 A/cm/sup 2/ is derived.     

120/spl deg/C 10-gb/s uncooled direct Modulated 1.3-/spl mu/m AlGaInAs MQW DFB laser diodes

A 1.3-/spl mu/m AlGaInAs multiquantum well ridge waveguide distributed feedback laser diode was developed. By forming n-InGaAsP grating in the n-InP cladding layer close to the active region, accumulation of the holes in the grating layer was reduced and over 5 mW of output power was obtained at 120/spl deg/C. Clear eye opening was confirmed with no mask hits for OC-192 under 10-Gb/s direct modulation at the temperature up to 120/spl deg/C.     

Narrow-beam and power-penalty-free 1.3-/spl mu/m laser diodes with monolithically integrated waveguide lens formed by selective-area epitaxial growth

A narrow-beam has been realized in a 1.3 /spl mu/m Fabry-Perot laser diode monolithically integrated with a tapered waveguide lens. The beam divergences in the perpendicular and horizontal directions are reduced down to 12/spl deg/ and 11/spl deg/ by a selective area epitaxial growth technique. The threshold current has been kept as low as 14 mA comparable to the conventional ones. Neither kinks in the L-I curves nor changes of far-field patterns are observed in the wide temperature range from -40 to 80/spl deg/C. Furthermore, high cut-off frequency over 4 GHz and power penalty-free characteristic under 622 Mb/s-50 km transmission have been confirmed.     

Optimization design of an electroabsorption modulator integrated with spot-size converter

In the recent years ,the electroabsorption modulator(EAM) is attractive as anexternal modulator because ofits many features ,such as low power consumption,lowdrive voltage,small size,large bandwidth,polarization-intensity and potential for monolithic integration withother components[1-3].An optical device integrated witha spot-size converter(SSC) has been paid more attentionfor its direct couplingto an optical fiber without using amicro-lens or tapered fiber[4].EAMintegrated with anSSC(EA…     

A continuous-wave hybrid AlGaInAs-silicon evanescent laser

We report a novel laser architecture, the hybrid silicon evanescent laser (SEL), that utilizes offset AlGaInAs quantum wells (QWs) bonded to a silicon waveguide. The silicon waveguide is fabricated on a silicon-on-insulator wafer using a complimentary metal-oxide-semiconductor-compatible process, and is subsequently bonded with the AlGaInAs QW structure using low temperature O/sub 2/ plasma-assisted wafer bonding. The optical mode in the SEL is predominantly confined in the passive silicon waveguide and evanescently couples into the III-V active region providing optical gain. The SEL lases continuous wave (CW) at 1568 nm with a threshold of 23 mW. The maximum temperature for CW operation is 60/spl deg/C. The maximum single-sided fiber-coupled CW output power at room temperature is 4.5 mW.     

Spatially singlemode broad-area semiconductor laser with planar external cavity

A broad-area laser diode combined with a planar external waveguide cavity operates in the fundamental mode and reshapes the output emission into a circular 15/spl deg/ beam. A 500 /spl mu/m-long by 40 /spl mu/m-wide laser diode with uncoated facets coupled with the uncoated ModeReShaper (MRS) planar chip has a coupling efficiency of /spl sim/40% and stabilised the fundamental mode at drive currents up to three-times threshold.     

High-power angled broad-area 1.3-/spl mu/m laser diodes with good beam quality

A new type of high-power laser diodes is fabricated with a broad-area waveguide tilted at 7/spl deg/ from the facet normal. For the current between 0.6 and 1.2 A, it behaves like a superluminescent diode with 40-nm spectral width and 40-mW output power. The far field emits at about 25/spl deg/ away from the facet normal. For the current above 1.2 A, it oscillates with a narrow spectrum. The far field emits along the facet normal with its angle only twice of the diffraction limit. The output power per facet could be 1 W at 12 A.     

Room-temperature continuous-wave operation of GaInNAsSb laser diodes at 1.55 /spl mu/m

The first 1.55 /spl mu/m room-temperature continuous-wave (CW) operation of GaAs-based laser diodes utilising GaInNAsSb/GaNAs double quantum well active regions grown by molecular beam epitaxy is reported. In electrically-pumped CW operation the narrow ridge waveguide devices have a room temperature lasing wavelength of 1550 nm near threshold, increasing to 1553 nm at thermal rollover. The CW threshold current was 132 mA for a 3/spl times/589 /spl mu/m device, with a characteristic temperature of 83 K, measured in pulsed mode between 20 and 70/spl deg/C.     

Lossless electroabsorption modulator monolithically integrated with a semiconductor optical amplifier and dual-waveguide spot-size converters

Semiconductor optical amplifier and electroabsorption modulator monolithically integrated with dual-waveguide spot-size converters at the input and output ports is demonstrated by means of selective area growth, quantum-well intermixing, and asymmetric twin waveguide technologies. At the wavelength range of 1550/spl sim/1600 nm, lossless operation with extinction ratios of 25-dB dc and 11.8-dB radio frequency and more than 10-GHz 3-dB modulation bandwidth is successfully achieved. The output beam divergence angles of the device in the horizontal and vertical directions are as small as 7.3/spl deg//spl times/10.6/spl deg/, respectively, resulting in 3.0-dB coupling loss with cleaved single-mode optical fiber.     

A fully integratable 1.55-/spl mu/m wavelength continuously tunable asymmetric twin-waveguide distributed Bragg reflector laser

We demonstrate a single-frequency continuously tunable three-section distributed Bragg reflector laser operating at a center wavelength of /spl lambda//sub 0/=1.548 /spl mu/m using a fully integratable asymmetric twin-waveguide structure. A low-loss tapered mode transformer couples the light between the active waveguide, or gain region, and the passive ridge waveguide where the phase and grating tuning sections are located. The device has a threshold current of 50 mA and output power of nearly 13 mW, with a slope efficiency of 0.12 W/A and a tuning range of 4.8 nm under pulsed operation. An independent phase section is used to continuously tune the wavelength, thus avoiding mode hops. Using a delayed self-heterodyne technique, we determine the linewidth to be (146/spl plusmn/2) kHz.     

Compact and low-loss arrayed waveguide grating module with tolerance-relaxed spot-size converter

A compact, low-loss arrayed waveguide grating (AWG) module was achieved by adopting a novel optical spot-size converter (SSC) to planar lightwave circuits (PLCs). The SSC is a laterally tapered waveguide that can be fabricated simply by the conventional fabrication process. The structure is composed of a core width converting region where the spot-size is converted efficiently, and a core width fine-tuning region where the cut-position tolerance is relaxed. We have applied this structure to a 1.5%-/spl Delta/ silica-based waveguides and reduced the single-mode fiber coupling loss to less than 0.5 dB/point. The SSC provides a large cut-position tolerance that enables angle polishing of the PLC endfaces to prevent reflection and low-loss connection of pigtail fibers. The center channel insertion loss of the AWG module was reduced from 4.2 to 2.2 dB, and the reflection was less than -60 dB.