Realisation of monolithically integrated single frequency MQW laser and booster amplifier at 1.5 mu m wavelength

The fabrication and performance of a 1.5 mu m wavelength multiquantum well distributed feedback laser monolithically integrated with a booster amplifier are described. Single longitudinal mode operation was achieved at output powers exceeding 45 mW. A minimum spectral linewidth of 2.3 MHz was obtained, with powers of 35 mW being reached before linewidth rebroadening occurred.<>     

Low-threshold and narrow-linewidth 1.5 mu m compressive-strained multiquantum-well distributed-feedback lasers

1.5 mu m compressive-strained multiquantum-well distributed-feedback lasers have been fabricated and characterised. 5.5 mA threshold current, 1 MHz mW linewidth-power product, and 600 kHz minimum linewidth were measured on 500 mu m long devices. Measured threshold current as low as 2.2 mA was also obtained on 150 mu m long devices. Both low threshold and narrow linewidth are attributed to the reduced transparency current and linewidth enhancement factor due to the effect of strain.<>     

Reduced linewidth re-broadening by suppressing longitudinal spatial hole burning in high-power 1.55-/spl mu/m continuous-wave distributed-feedback (CW-DFB) laser diodes

For the first time, the impact of longitudinal photon density distribution and longitudinal carrier density distribution on the spectral linewidth re-broadening effect in single-electrode 1.55-/spl mu/m distributed feedback (DFB) laser diodes (LDs) is investigated experimentally in details. By optimizing the front-to-rear facet power ratio, the nonuniformity of the photon density distribution along the laser cavity is reduced, hence reducing the degree of longitudinal spatial hole burning (SHB). Using this optimized value of front-to-rear facet power ratio, the degree of longitudinal SHB can be further reduced through reduction of the nonuniformity of the longitudinal carrier density distribution by increasing the cavity length. As a result, the local stimulated emission is reduced, hence reducing linewidth re-broadening caused by longitudinal SHB. The outcomes of this analysis is being used fruitfully to design high-power 1.55-/spl mu/m DFB LDs exhibiting very narrow spectral linewidth of approximately 1.3 MHz at an output power of 175 mW under continuous-wave operation.     

Tunable twin-guide (TTG) distributed feedback (DFB) laser with over 10 nm continuous tuning range

By exploiting electronic and thermal tuning by forward and backward biasing the tuning region, a record continuous tuning range of 11nm has been achieved with an improved strained-layer (SL) multiquantum-well (MQW) TTG DFB laser at 1.55 mu m wavelength. Over a wavelength range of 9.2nm an optical power above 1mW and a spectral linewidth below 30MHz can be maintained with 400 mu m long devices.<>     

Narrow linewidth (85 kHz) operation in long cavity 1.5 mu m-MQW DBR laser

An extremely narrow linewidth of 85 kHz operation was obtained at 10 mW output power in a 2.16 mm long, 1.5 mu m-MQW DBR laser. This is the narrowest linewidth ever reported in a semiconductor laser diode without an external cavity.<>     

Linewidth of InP-based 1.55 /spl mu/m VCSELs with buried tunnel junction

Spectral linewidth measurements of 1.55 /spl mu/m InGaAlAs/InP vertical-cavity surface-emitting lasers (VCSELs) employing a buried tunnel junction are reported. A narrow linewidth around 28 MHz was obtained at a power level of 0.5 mW using the self-heterodyne method, and an estimation for the linewidth enhancement factor is given.     

Extremely narrow linewidth ( approximately 1 MHz) and high-power DFB lasers grown by MOVPE

A suitable structure of narrow linewidth DFB laser is studied experimentally. By thinning the active layer to around 0.07 mu m, controlling kappa L to 1.0, and improving the geometrical uniformity of active region, the linewidth less than 1 MHz is achieved at an output power of around 20 mW in 1.55 mu m DFB lasers with 1.2 mm long cavity length.<>     

Highly stable low-noise Brillouin fiber laser with ultranarrow spectral linewidth

We demonstrate an all-fiber high-power single-frequency Brillouin fiber ring laser with maximum power of 100 mW at 1.55 /spl mu/m, which is actively stabilized by using the Pound-Drever-Hall frequency-locking scheme. Significant reduction (/spl sim/20dB) of both relative intensity noise and frequency noise was observed in the Brillouin Stokes radiation as compared with those noises of its pump source, a narrow-linewidth Er-doped fiber laser. Ultranarrow spectral linewidth of the Brillouin fiber lasers was investigated by both delayed self-heterodyne technique and heterodyne beat technique between two independent Brillouin fiber lasers.     

Linewidth study of InAs-InGaAs quantum dot distributed feedback lasers

The linewidth of laterally loss-coupled distributed feedback (DFB) lasers based on InAs quantum dots (QDs) embedded in an InGaAs quantum well (QW) is investigated. Narrow linewidth operation of QD devices is demonstrated. A linewidth-power product less than 1.2 MHz /spl middot/ mW is achieved in a device of 300-/spl mu/m cavity length for an output power up to 2 mW. Depending on the gain offset of the DFB modes from the QD ground state gain peak, linewidth rebroadening or a floor is observed at a cavity photon density of about 1.2-2.4/spl times/10/sup 15/ cm/sup -3/, which is much lower than in QW lasers. This phenomenon is attributed to the enhanced gain compression observed in QDs.     

Spectral linewidth estimation of a 1.5 µm range InGaAsP/InP distributed feedback laser

Spectral linewidth of a 1.5 μm range distributed feedback buried heterostructure (DFB-BH) laser in CW operation is estimated theoretically and experimentally. Considering the equivalent mirror facet loss coefficient and the confinement factor in the active layer, etc., we modified the conventional formula for the spectral linewidth of single-mode semiconductor lasers and presented a formula for the linewidth of DFB lasers. Furthermore, power-dependent linewidth measurements of a 1.5 μm range InGaAsP/InP DFB-BH laser with a window region were carried out using Fabry-Perot interferometers. The linewidth was observed to increase linearly with inverse output power. The measured result was explained by the calculated result through the modified formula. The full width at half maximum was estimated to be 50 MHz at an output power of 1 mW.     

Narrow linewidth and low chirping characteristics in high poweroperating butt-jointed DBR lasers grown by MOVPE

High power operation in 1.5 μm butt-jointed DBR lasers, made entirely by MOVPE is demonstrated. An output power of more than 30 mW and 60 mW is observed in the CW and pulsed condition, respectively. The minimum spectral linewidth achieved here is 2.1 MHz, at an output power of 12.5 mW and the wavelength chirping width under NRZ modulation is 60-70% of that of conventional DFB lasers     

Erbium-doped fluorozirconate single-mode fibre lasing at 2.71 mu m

Continuous-wave lasing has been obtained at 2.714 mu m in a fluorozirconate single-mode fibre when pumping at 476.5, 501.7 or 647.1 nm. A threshold pump power of 7 mW, an output laser power of 250 mu W and a linewidth less than 2 nm were measured.<>     

High performance 1.5 mu m multiple-quantum-well DFB-DC-PBH-LDs at 30 mW output power for Gb/s range coherent systems

Long cavity (1200 mu m) MQW-DFB-DC-PBH-LDs have been developed. The devices simultaneously showed less than 1 MHz spectral linewidth, lower than 15 kHz FM dip frequency, moderate FM efficiency (250-300 MHz/mA at 100 MHz modulation frequency), as well as 10-GHz FM bandwidth (6 dB down level from the peak), at 30 mW output power condition. Such LDs will be suitable for Gb/s continuous phase frequency shift keying (CPFSK) current optical fiber communication systems.<>     

Fabrication approach for antiphase narrow linewidth complex coupled 1.55 /spl mu/m DFB lasers

A new method for fabricating narrow linewidth antiphase complex coupled MQW DFB lasers by periodically etching the active layer and quarternary InGaAsP overgrowth is reported. The minimum linewidth for a 375 /spl mu/m long ridge waveguide laser is only 250 kHz at an optical output power of 4 mW.     

A compact nine-channel multiwavelength laser

A phased-array-based multiwavelength laser has been realized on a chip area of 3.5/spl times/2.5 mm/sup 2/. The device has nine channels, spaced at 400 GHz around a central wavelength of 1.55 /spl mu/m. Its performance is characterized by a minimum threshold current of 101 mA, a maximum fiber-coupled power of 0.37 mW, and a linewidth of 21 MHz. In addition, simultaneous four-channel operation is demonstrated.     

Low-threshold 1.5 mu m DFB laser grown by GSMBE

GaInAsP 1.5 mu m DFB lasers with a low threshold current (17 mA) have been grown by gas source molecular beam epitaxy (GSMBE) in a two-step epitaxial process. The lasers exhibit single-mode emission for emitted power in excess of 10 mW with side mode suppression ratio of 40 dB and spectral linewidth of 15 MHz. In addition the dispersion of the lasing wavelength has been found to be as low as 1.7 nm.<>     

Spectral linewidth of AlGaAs/GaAs surface-emitting laser

The spectral linewidth Delta nu of a vertical cavity surface-emitting (SE) laser was measured for the first time. The linewidth measured by a delayed self-homodyne method was 50 MHz at an output power of 1.4 mW under room-temperature CW operation. The linewidth obtained was guite narrow in spite of the short cavity configuration of the SE laser. This narrow linewidth is attributed to the high-reflectivity mirrors. The measured linewidth is in good agreement with theoretical values.<>     

High-power highly reliable 1.02-1.06-/spl mu/m InGaAs strained-quantum-well laser diodes

By growing the InGaAs active layer at temperatures lower than in conventional growth, we extended the lasing wavelength and presented the high reliability in InGaAs strained-quantum-well laser diodes. Equivalent I-L characteristics were obtained for 1.02-, 1.05-, and 1.06-/spl mu/m laser diodes with a cavity length of 1200 /spl mu/m. Maximum output power as high as 800 mW and fundamental transverse mode operation at up to 400 mW were obtained at 1.06 /spl mu/m and an 1800-/spl mu/m cavity. Stable operation was observed for over 14 000 h under auto-power-control of 225 mW at 50/spl deg/C for the 1.02-, 1.05-, and 1.06-/spl mu/m lasers with a 900-/spl mu/m cavity.     

A 25 ns 8K /spl times/ 8 static MTL/I/SUP 2/L RAM

An experimental 8K /spl times/ 8-bit static MTL RAM has been successfully fabricated in a standard bipolar manufacturing process with 2-/spl mu/m epitaxy and junction isolation, using design rules of 2.2 /spl mu/m minimum dimensions. Despite conservative processing and less aggressive photolithography compared to the most advanced static FET RAMs, a significantly better performance of 25-ns access has been achieved at a comparable bit density of 1730 bits/mm/SUP 2/. Another outstanding feature is the very low power dissipation of only 8 mW in standby and 270 mW at 50-ns or 150 mW at 100 ns-cycle operation. A holding power below 1/spl mu/W has been measured to retain the information in the complete cell array. A further significant advantage is the insensitivity to /spl alpha/-particle radiation which is a characteristic of the MTL structure.     

Integrated low-noise lasers

Using new small-signal analytic relations, the linewidth, amplitude fluctuations, main-mode transient response and photon-electron ringing frequency are presented for a laser with fixed active length and variable-length passive region joined with negligible reflection. With 150 ?m active length and 1000 ?m total length, a linewidth below 1 MHz is achievable at 5 mW output.