Bandwidth enhancement of injection-locked 1.3 μm quantum-dot DFB laser

Optical injection locking of a quantum-dot distributed-feedback laser at 1.3 mum is reported. Using an injection ratio of 5.3 dB, an optical detuning of -40 pm, and a slave laser biased at 20 mA, the modulation bandwidth of the injection-locked laser was 16.3 GHz. This is over four times higher than the modulation bandwidth of the free-running quantum-dot laser. At a slave laser bias of 5.0 mA, injection locking resulted in a resonance frequency of 21.9 GHz, over eleven times higher than the relaxation frequency of the free-running slave laser.     

Room-temperature continuous-wave operation of type-I GaSb-based lasers at 3.1 μm

Type-I interband lasers on GaSb were grown by molecular beam epitaxy using 16 nm InGaAsSb compressively-strained quantum wells (QWs) with 30 nm AlInGaAsSb quinary barriers for improved hole confinement. The 3QW active regions were embedded in standard AlGaAsSb waveguides to limit the thickness of quinary material owing to its low growth temperature requirements. In continuous-wave operation, a typical ridge waveguide laser (width 10 mum, length 1214 mum) produced 6 mW total output power at 20degC with a threshold current of 140 mA. The temperature sensitivity of the devices remains a challenge, as evidenced by the dramatically improved performance at 0degC (16 mW total output power, threshold current 74 mA).     

Power efficient Ka-band low phase noise VCO in 0.13 μm CMOS

A 27 GHz cross-coupled LC voltage controlled oscillator (VCO) using a standard 0.13 mum CMOS technology is presented. The VCO using a high-Q LC resonator with a micro-strip inductor (mu-strip L) provides a phase noise of -113 dBc/Hz at a 1 MHz offset frequency. The figure - of-merit (FoM) is -194.6 dBc/Hz. To obtain high output power, it also uses a common source amplifier as a buffer and it shows the output power of -3.5 dBm at an oscillation frequency of 26.89 GHz. This is believed to be the lowest phase noise and FoM with the highest output power of a millimetre-wave VCO in CMOS technology.     

Low threshold current density 1.3 μm metamorphic InGaAs/GaAs quantum well laser diodes

Very low threshold current density InGaAs/GaAs quantum well laser diodes grown by molecular beam epitaxy on InGaAs metamorphic buffers are reported. The lasing wavelength of the ridge waveguide laser diode with cavity length of 1200 mum is centered at 1337.2 nm; the threshold current density is 205 A/cm² at room temperature under continuous-wave operation.     

Room-temperature singlemode continuous-wave operation of distributed feedback GaInNAs laser diodes at 1.5 μm

Room-temperature continuous-wave operation of distributed feedback GalnNAs quantum well laser diodes on GaAs in the 1.5 mum wavelength range is demonstrated for the first time. Singlemode emission with a sidemode suppression ratio of more than 45 dB is obtained at 1486 nm with a threshold current of 44 mA and an external efficiency of 0.06 W/A.     

Singlemode emission at 2 μm wavelength with InP based quantum dash DFB lasers

Long wavelength distributed feedback (DFB) laser diodes based on InP quantum dash-in-a-well material have been fabricated and investigated at room temperature under continuous-wave operation. Singlemode emission of InP laser diodes at wavelengths above 2 mum is demonstrated for the first time.     

Design of UWB switched gain controlled LNA using 0.18 μm CMOS

A switched gain controlled low noise amplifier (LNA) for the 3.1- 4.8 GHz ultra-wideband system is presented. The LNA is fabricated with the 0.18 mum 1P6M standard CMOS process. Measurement of the LNA was performed using an RF probe station. In gain mode, measured results show a noise figure of 4.68-4.97 dB, gain of 12.5-13.9 dB, and input/output return loss higher than 10/8.2 dB. The input IP3 (IIP3) at 4.1 GHz is 1 dBm, and consumes 14.6 mW of power. In bypass mode, measured results show a gain of-7.0 to -8.7 dB, and input/output return loss higher than 10/6.3 dB. The input IP3 at 4.1 GHz is 9.2 dBm, and consumes 1 muW of power.     

Butt joint integrated extended cavity InAs/ InP (100) quantum dot laser emitting around 1.55 μm

The first butt joint integrated extended cavity InAs/InP (100) quantum dot (QD) Fabry-Perot laser emitting around 1.55 mum is demonstrated. Continuous wave lasing at room temperature on the QD ground state transition is achieved. The threshold current is comparable to that of all-active QD lasers. The Butt joint reflectivity for straight waveguides is below -40 dB.     

GaSb-based monolithic EP-VCSEL emitting above 2.5 μm

The 2 to 3 mm mid-infrared wavelength range is a wellknown transparence window of the atmosphere which contains absorbing lines of numerous polluting gases such as CO, CH/sub 4/, NH/sub 3/ and HF. Currently, one of the more precise gas sensing techniques is tunable diode laser absorption spectroscopy (TDLAS) which measures the absorption of a singlemode laser beam to detect the presence or not of absorbing gases. The realisation of a highly precise trace-gas TDLAS sensing system thus implies the development of specific laser sources exhibiting adapted properties. Electrically-pumped vertical cavity surface emitting lasers (EP-VCSELs) appear particularly well suited to be such laser sources owing to several advantages they offer such as small beam divergence, singlemode operation, fast and far wavelength tunability without mode hops, low threshold, high rate of modulation and less susceptibility to optical feedback [1, 2]. To date, Sb-based heterostructures allow coverage of a major part of the 2 to 4 mm mid-infrared wavelength [3] range. Moreover, recent progress on RT electrically-pumped GaSb-based VCSELs emitting up to 2.3 mm were obtained [4, 5]. However, this wavelength of emission remains the longest ever reported fromany semiconductor EP-VCSELs. In this Letter, the first result of an all-epitaxial monolithic EP-VCSEL emitting at 2.52 mm in quasi-CWregime at room temperature is described.     

GaAs-based 1.53 μm GaInNAsSb vertical cavity surface emitting lasers

Electrically-pumped GaAs-based 1.53 mum vertical cavity surface emitting lasers operating in pulsed mode at room temperature and continuous wave (CW) up to 20degC are reported for the first time. The lasers employ a GaInNAsSb/GaNAs multiple quantum well active region, a selectively oxidised AlAs aperture and p- and n-doped Al(Ga)As/GaAs distributed Bragg reflectors. Typical devices have room-temperature pulsed threshold current densities of 8.3 kA/cm and threshold voltages of 5.5 V. CW threshold currents as low as 2.87 mA for a 7 mum aperture device were observed at 15degC.     

Micromechanical resonators with submicron capacitive gaps in 2 μm process

An innovative gap reduction technique is reported to achieve sub-micron capacitive gaps for micromechanical resonators to boost the output signal using the standard low-cost 2 mum commercially available foundry process from MEMSCAP. Electrostatic actuation was used to reduce the gap size below the fabrication limitation. To demonstrate the proposed idea, a 6.35 MHz Lame-mode square resonator was designed, fabricated and tested. The resonator gap size was experimentally measured to be 0.64 mum, which boosted the resonance peak by 20 dB.     

Lead chalcogenide VECSEL on Si emitting at 5 μm

A mid-infrared vertical external cavity surface emitting laser (VECSEL) on a Si substrate has been realised. It is optically pumped and emits around 5 μm wavelength. Maximum output power of 26 mW_p (limited by the 1.5μm wavelength pump laser) was observed at 100 K operating temperature with 3μs pulse widths. The active part is just a 1.3μm-thick PbTe layer.     

Very low threshold current density 1.29 μm GaInNAs triple quantum well lasers grown by MBE

Very low threshold Ga_0.62In_0.38N_0.007As_0.993/GaN_0.011As_0.989/GaAs triple quantum well (QW) lasers emitting at 1.29 mum are demonstrated. The laser structure was grown by molecular beam epitaxy after extensive optimisations of growth and in situ annealing conditions. As- cleaved broad area lasers with a cavity length of 1 mm showed a record low threshold current density of 400 A/cm² (~130 A/cm² / QW), a high differential efficiency of 0.32 W/A/facet and a characteristic temperature of 94 K in the temperature range 10 to 110degC.     

Very-low-threshold current density 1.29 μm GaInNAs triple quantum well lasers grown by molecular beam epitaxy

Very-low-threshold Ga_0.62In_0.38N_0.007As_0.993/GaN_0.011 As_0.989/GaAs triple quantum well (QW) lasers emitting at 1.29 mum are demonstrated. The laser structure was grown by molecular beam epitaxy after extensive optimisations of growth and in situ annealing conditions. As-cleaved broad-area lasers with a cavity length of 1 mm under pulsed operation showed a record low-threshold current density of 400 A/cm² (~130A/cm²/QW), a high differential efficiency of 0.32 W/A/facet and a characteristic temperature of 94 K in the temperature range 10 to 110degC.     

Relative intensity noise measurements of a widely tunablesampled-grating DBR laser

The intensity noise of a sampled-grating distributed Bragg reflector laser with 50-nm tuning range and 45-dB side-mode suppression ratio has been measured. The resonance frequency, damping factor, and modified Schawlow-Townes linewidth are extracted from the noise spectra. At high output power, the relative intensity noise (RIN) of the laser is below the photodiode shot noise limit, which is -160 dB/Hz. The laser has uniform shot noise limited RIN properties along the whole tuning range. The maximum resonance frequency is 5.4 GHz at a bias current of 120 mA and the K factor is 0.58 ns     

0.18 μm 3.1-10.6 GHz CMOS UWB LNA with 11.4±0.4 dB gain and 100.7± 17.4 ps group-delay

A3.1-10.6 GHz ultra-wideband low-noise amplifier (UWB LNA) with excellent phase linearity property (group-delay-variation is only plusmn17.4 ps across the whole band) using standard 0.18 mum CMOS technology is reported. To achieve high and flat gain and small group-delay-variation at the same time, the inductive peaking technique is adopted in the output stage for bandwidth enhancement. The UWB LNA dissipates 22.7 mW power and achieves input return loss (S₁₁) of -9.7 to -19.9 dB, output return loss (S22) of-8.4 to -22.5 dB, flat forward gain (S21) 11.4 plusmn0.4 dB, reverse isolation (S12) of -40 to -48 dB, and noise figure of 4.12-5.16 dB over the 3.1-10.6 GHz band of interest. A good 1 dB compression point (Pi dB) of -7.86 dBm and an input third-order intermodulation point (IIP3) of 0.72 dBm are achieved at 6.4 GHz. The chip area is only 681 x 657 mum excluding the test pads.     

High-power InGaAs/GaAs 1.3 μm VCSELS based on novel electrical confinement scheme

Reported are 1.3 mum InGaAs/GaAs vertical-cavity surface-emitting lasers (VCSELs) with a novel electrical confinement scheme based on lithographic definition and selective area epitaxial regrowth in the cavity region. More than 6 mW of output power with a record high differential efficiency of more than 70% is emitted from 10 mum large devices.     

Operation of diode laser pumped Tm3+ ZBLAN upconversionfiber laser at 482 nm

Lasing at 482 nm is observed in Tm³⁺-doped ZBLAN glass fiber pumped with single-mode InP semiconductor diode lasers. Up to 5 mW of 482 nm light is obtained with <40 mW of absorbed pump power from a single 1135 nm pump diode laser. The optimum pump wavelength is measured to be 1135-1340 nm. More efficient laser operation is observed in fiber with 2500 ppm Tm³⁺ compared to 1000 ppm Tm³⁺ because of the reduced length of the fiber laser cavity possible with increased doping. Improved slope efficiencies are also demonstrated when the fiber laser is co-pumped with up to 5 mW from a 1220 nm diode laser. The relative intensity noise (RIN) of the fiber laser displays a maximum of -90 dB/Hz at relaxation oscillation frequencies of a few tens of kHz. The measurement of RIN is limited by shot-noise of -152 dB/Hz above 2 MHz. At higher frequencies, self mode-locking was observed in the fiber laser, which may indicate the existence of saturable absorbers in the fiber core. The presence of such bleachable absorbers is indicated by the observed increase in threshold after upconversion lasing at 482 mm     

Low-noise narrow-linewidth fiber laser at 1550 nm (June 2003)

We present a compact integrated fiber laser with more than 200 mW of output power. It combines polarized fiber output with very narrow linewidth of less than 2 kHz. The coherence length of the laser is measured to be longer than 5 km. The laser features high mode stability of less than /spl plusmn/10 MHz over hours. The relative intensity noise (RIN) spectrum is dominated by a peak at the relaxation oscillation frequency and is shot-noise limited otherwise. The RIN peak at 1 MHz is reduced to /spl sim/-130 dB/Hz by integrating a negative feedback circuit. In addition to thermal wavelength tuning, the laser frequency can be modulated at a bandwidth of up to 10 kHz via the piezoelectric effect.     

Manufacturing of laser diode modules: Integration and automation of laser diode-fiber alignment and RIN characterization

Laser diode-fiber alignment and relative intensity noise (RIN) characterization are two crucial steps to the manufacturing of fiber pigtailed laser diode modules. Integrating both steps into a single automatic process can increase yield, improve the throughput and reduce manufacturing cost. This work presents a novel scheme of the integrated laser-diode-to-fiber alignment and RIN testing automation for the manufacturing of Fabry-Perot (FP) laser diode module hosted in a low cost isolator-free coaxial-type package. It is demonstrated that the value of RIN is not only determined by the intrinsic spontaneous emission of the laser diode, but also strongly dependent on the fiber-laser alignment and pigtailing process. It is experimentally determined, for the first time, that regardless of the type of lensed fiber employed for fiber-laser coupling, and with or without the presence of angular misalignment, there is an optimal fiber-laser alignment location at which the RIN value reaches its minimum. Moreover, it is observed that both RIN minimization and laser power coupling maximization occur at the same fiber-laser alignment position.