Fabrication of AlGaAs-GaAs quantum-wire gain-coupled DFB lasers bya single MOCVD growth step

AlGaAs-GaAs quantum-wire (QWR) gain-coupled distributed-feedback (GC-DFB) lasers have been fabricated by a single metal-organic chemical vapor deposition growth step on 0.36-μm pitch V-groove arrays of GaAs. A record low-threshold current of 13 mA is achieved via DFB lasing from QWR gain at room temperature. The consistency of the photon energies of the lasing and the photoluminescence peaks from QWR, and about 4-nm-wide stopband with a large threshold gain difference observed in the near-threshold spectrum are presented as possible evidence for GC-DFB effects in these devices     

Analysis of the response of long period fiber gratings to externalindex of refraction

This paper demonstrates that the change in wavelength of a long period fiber grating attenuation band with changes in external index of refraction can be enhanced by proper selection of the grating period. We calculate and experimentally verify that the wavelength shift caused by changing the external index from n=1 to n=1.44 of the attenuation band which appears in the 1400-1600 nm region in a 200-μm period grating is four times that in a 350-μm period grating. Changes in the spectrum over a wavelength range from 1100 to 1600 nm and 1相似文献   

Light-emitting diode emitting at 650 nm with 200-MHz small-signalmodulation bandwidth

State-of-the-art modulation bandwidths are presented for multiquantum well resonant cavity light emitting diodes (RCLED's) emitting at 650 nm. 84-μm size epoxy coated RCLED's have a 1.4-mW (CW) output power and a small signal modulation bandwidth of 200 MHz at 40 mA bias. 150-μm diameter devices yield 3.25-mW and 150-MHz bandwidth at 70-mA bias. An open eye-diagram at 622 Mb/s achieved for the 84-μm device makes it very attractive for SONET OC-12 data communication links     

High T0 long-wavelength InGaAsN quantum-well lasersgrown by GSMBE using a solid arsenic source

We demonstrate high performance, λ=1.3- and 1.4-μm wavelength InGaAsN-GaAs-InGaP quantum-well (QW) lasers grown lattice-matched to GaAs substrates by gas source molecular beam epitaxy (GSMBE) using a solid As source. Threshold current densities of 1.15 and 1.85 kA/cm² at λ=1.3 and 1.4 μm, respectively, were obtained for the lasers with a 7-μm ridge width and a 3-mm-long cavity. Internal quantum efficiencies of 82% and 52% were obtained for λ=1.3 and 1.4 μm emission, respectively, indicating that nonradiative processes are significantly reduced in the quantum well at λ=1.3 μm due to reduced N-H complex formation. These Fabry-Perot lasers also show high characteristic temperatures of T₀ =122 K and 100 K at λ=1.3 and 1.4 μm, respectively, as well as a low emission wavelength temperature dependence of (0.39±0.01) nm/°C over a temperature range of from 10°C to 60°C     

Continuous-wave mid-infrared VCSELs

We report the continuous-wave operation of an optically pumped mid-infrared (mid-IR) vertical-cavity surface-emitting laser (VCSEL). The active region consisting of type-II antimonide quantum wells with a “W” configuration occupies a cavity formed by a semiconductor bottom mirror and dielectric top mirror. The emission wavelength of 2.9 μm is nearly independent of temperature (dλ/dT≈0.09 nm/K) compared to type-II edge-emitters and the multimode linewidth is narrow (2.9 nm). At T=78 K, the threshold pump intensity is ≈940 W/cm², the peak output power from a 50-μm spot is 45 mW, and the differential power conversion efficiency is 4.5%. Lasing is observed up to T=160 K     

Design optimization for efficient erbium-doped fiber amplifiers

The gain and pumping efficiency of aluminosilicate erbium-doped fiber amplifiers (EDFAs) are analyzed as a function of guiding parameters and Er-doping profile for two pump wavelengths of λ _p=980 nm and λ_p=1.47 μm. Three designs of fiber-amplifier waveguides are considered: one with the same mode size as standard 1.5-μm communication fibers (type 1); one with the same mode size as standard 1.5-μm dispersion-shifted fibers (type 2); and one with mode size smaller than those of communication fibers (type 3). For the 1.47-μm pump, fundamental LP₀₁ mode excitation is assumed, while for the λ_p=980-nm pump, concurrent excitation of LP₁₁ modes is considered. It is shown that excitation of higher-order pump modes at 980 nm does not significantly affect the amplifier gain performance. The effect of concentrating the Er³⁺ doping near the center of the fiber core is shown to increase the amplifier gain coefficients by a factor of 1.5 to 2     

1.2-μm GaAsP/InGaAs strain compensated single-quantum-well diodelaser on GaAs using metal-organic chemical vapor deposition

We demonstrate here 1.2-μm laser emission from a GaAsP-InGaAs strain compensated single-quantum-well (SQW) diode. This development enables the fabrication of vertical-cavity surface-emitting lasers for optical interconnection through Si wafers. Strain compensation and low temperature growth were used to extend the wavelength of emission to the longest yet achieved on a GaAs substrate in this materials system. The minimum threshold density achieved was 273.4 A/cm² at a cavity length of 610 μm. We have also demonstrated an 1.144-μm lasing wavelength in a 820-μm-long cavity on a GaAs substrate with a strained InGaAs-GaAs SQW laser for comparison using a low-temperature metal-organic chemical vapor deposition growth technique. The threshold current density for a 590-μm-long cavity under CW operation was 149.7 A/cm²     

Wide-range tunable semiconductor lasers using asymmetric dualquantum wells

Using asymmetric dual quantum wells for the laser material, the semiconductor lasers are broadly tunable. In a grating coupled ring cavity, the semiconductor laser is continuously tunable from 766 to 856 nm using a 400-μm semiconductor laser amplifier in the cavity. This letter also demonstrates that the grating coupled ring cavity could well eliminate the amplified stimulated emission noise and about 40-dB amplified spontaneous emission (ASE) suppression ratio is obtained over the entire tuning range     

1.58-μm band gain-flattened erbium-doped fiber amplifiers forWDM transmission systems

This paper describes the amplification characteristics of gain-flattened Er³⁺-doped fiber amplifiers (EDFAs) by using 0.98-μm and 1.48-μm band pumping for a 1.58-μm band WDM signal. Silica-based Er³⁺-doped fiber (S-EDF) and fluoride-based Er ³⁺-doped fiber (F-EDF) have gain-flattened wavelength ranges from 1570 to 1600 nm and from 1565 to 1600 nm, respectively, and exhibit uniform gain characteristics with gain excursions of 0.7 and 1.0 dB, and the figure of merit of the gain flatness (gain excursion/average signal gain) of 3 and 4.3%, respectively, for an eight-channel signal in the 1.58-μm band. We show that 1.48-μm band pumping has a better quantum conversion efficiency and gain coefficient, and that 0.98-μm band pumping is effective for improving the noise characteristics. We also show that the EDFAs consisting of two cascaded amplification units pumped in the 0.98-μm and 1.48-μm bands are effective in constructing low-noise and high-gain 1.58-μm band amplifiers     

Single-mode operation of mushroom structure surface emitting lasers

Mushroom structure vertical cavity surface emitting lasers with a 0.6-μm GaAs active layer sandwiched by two Al_0.6Ga_0.4 As-Al_0.08Ga_0.92As multilayers as top and bottom mirrors are discussed. The lasers exhibit a 15-mA pulses threshold current at 880 nm. Single longitudinal and single transverse mode operation was achieved on lasers with a 5-μm-diameter active region of current levels near 2×l_th. The light output above threshold current was linearly polarized with a polarization ratio of 25:1     

Operating characteristics of high continuous power (50 W)two-dimensional surface-emitting lase array

Monolithic two-dimensional surface-emitting laser (SEL) arrays suitable for both optoelectronic and high power applications were fabricated utilizing a 4-μm×450-μm InGaAs single mode real refractive index guided gain cavity with 90° and 45° ion milled facets. A total CW output power exceeding 50 W was achieved at λ≈944 nm from a monolithic 16×94 2-D SEL array. The 50-W CW output power level is approximately ten times greater than previously demonstrated from a 2-D monolithic SEL array. Greater than 150 h of continuous operation of a 2-D SEL array at 25 W CW was demonstrated     

The effects of source/drain resistance on deep submicrometer deviceperformance

As MOSFET channel lengths approach the deep-submicrometer regime, performance degradation due to parasitic source/drain resistance (R _sd) becomes an important factor to consider in device scaling. The effects of R_sd on the device performance of deep-submicrometer non-LDD (lightly doped drain) n-channel MOSFETs are examined. Reduction in the measured saturation drain current (R_sd=600 Ω-μm) relative to the ideal saturation current (R_sd=0.0 Ω-μm) is about 4% for L_eff=0.7 μm and T_ox =15.6 nm and 10% for L_eff=0.3 μm and T _ox=8.6 nm. Reduction of current in the linear regime and reduction of the simulated ring oscillator speed are both about three times higher. The effect of salicide technologies on device performance is discussed. Projections are made of the ultimate achievable performance     

Scaled CMOS technologies with low sheet resistance at 0.06-μmgate lengths

A novel Ti self-aligned silicide (salicide) process using a combination of low dose molybdenum and preamorphization (PAI) implants and a single rapid-thermal-processing (RTP) step is presented, and shown to be the first Ti salicide process to achieve low sheet resistance at ultrashort 0.06-μm gate lengths (mean=5.2 Ω/sq, max=5.7 Ω/sq at 0.07 μm; mean=6.7 Ω/sq, max=8.1 Ω/sq at 0.06 μm, TiSi₂ thickness on S/D=38 nm), in contrast with previous Ti salicide processes which failed below 0.10 μm. The process was successfully implemented into a 1.5 V, 0.12-μm CMOS technology achieving excellent drive currents (723 and 312 μA/μm at I_OFF=1 nA/μm for nMOS and pMOS, respectively)     

Selective lasing of InGaAs quantum-wire array on a V-grooved GaAssubstrate by distributed optical feedback

Distributed-feedback (DFB) lasers were fabricated by using strained InGaAs quantum-wire (QWR) arrays on V-grooved GaAs substrates as an active grating. After characterizing the luminescence from the QWRs and parasitic quantum wells (QWLs), a DFB laser cavity incorporating such a QWR array with its emission wavelength matched to the Bragg wavelength was designed and fabricated. The wavelength selectivity of the DFB cavity was found to strongly support the QWR emission, and DFB lasing from QWR gain up to 145 K has been achieved under pulsed current. The emission from the parasitic QWLs was suppressed by the DFB filtering and the loss induced by coupling to radiation modes. The DFB cavity was shown to be essential for obtaining lasing from QWRs on V-grooved substrates     

Broadly wavelength-tunable external cavity, mid-infrared quantumcascade lasers

Wavelength tuning over 120 nm for a grating-coupled 5.1-μm quantum-cascade type-I laser was studied for temperature from 80 to 243 K (-30°C). Both the Littman-Metcalf and first-order grating direct feedback cavity configurations were used with similar tuning results. The goal is to achieve broad tunability, and the result is a combined grating and temperature tuning of 245 nm, from 5.040 to 5.285 μm. The laser was designed for predominantly single-mode or at most, two-longitudinal mode operation. The instrument-limited laser linewidth was less than the cavity longitudinal mode spacing. Stepping-motor control of the grating allowed 0.4-GHz wavelength increments (35 pm) to be realized with high reproducibility. A current-induced wavelength shift of ~2-3 GHz was observed, corresponding to an effective refractive index change of ~10^-3. Analysis indicates that single-mode, continuously tunable operation is feasible with a more optimal device and cavity     

Improving single-mode VCSEL performance by introducing a longmonolithic cavity

We report on the improvement of several selectively oxidized vertical-cavity surface emitting laser characteristics by introducing a long monolithic cavity. The samples compared are grown with various cavity lengths using solid-source MBE. The 980 nm-regime is chosen as emission wavelength to facilitate growth by using binary GaAs cavity spacers. A record high single-transverse mode output power of 5 mW at a series resistance of 98 Ω is obtained for a 7-μm aperture device with a 4-μm cavity spacer. Using an 8-μm cavity spacer, devices up to 16-μm aperture diameter emit 1.7 mW of single-mode power with a full-width at half-maximum far-field angle below 3.8°     

Design and fabrication of low-threshold 1.55-μm graded-indexseparate-confinement heterostructure strained InGaAsPsingle-quantum-well laser diodes

This paper presents a guideline for designing an optimum low-threshold 1.55-μm graded-index (GRIN) separate confinement-heterostructure (SCH) strained InGaAsP single quantum-well (SQW) laser diode (LD). The guideline was formulated based on the results of numerical and experimental analysis. After calculating the sheet carrier density at the lasing threshold, the guideline was obtained by considering the tradeoff between carrier and optical confinements in the well: the GRIN layer energy gap should be varied parabolically from InP to InGaAsP having a band gap wavelength of 1.1 μm to inject a large number of carriers into the well, and the thickness of one side of the GRIN layer should be more than 300 nm to keep a strong optical confinement. The GRIN SQW LD designed using the guideline has a J_th as low as 98 A/cm² at a cavity length of 5 mm, which proves the guideline is effective for designing low-threshold 1.55-μm GRIN SQW LDs     

Laser diode-pumped holmium-doped fluorozirconate glass fiber laserin the green (λ~544-549 nm): power conversion efficiency, pumpacceptance bandwidth, and excited-state kinetics

The green (544-549 nm) Ho-doped fluorozirconate (ZBLAN) glass fiber laser, pumped in the red (λ~6;15 nm) by a high-power (~30 mW) InGaAlP laser diode or a ring dye-laser, has been characterized with regard to power conversion efficiency, fiber core-diameter and length, cavity output coupling, and pump acceptance bandwidth. Fibers doped with ~1200 ppm (by weight) of Ho and having core diameters of 1.7, 3, and 11 μm, and lengths ranging from 12.5 to 86 cm, have been studied in Fabry-Perot resonators having output couplings ranging from 1.545 to 96%. For a 1.7-μm core-diameter fiber, 21 cm in length, the threshold-launched pump power for the diode-pumped fiber laser is 1.9 and 3.5 mW for cavity output couplings of 1.5% and 24%, respectively. These values are the lowest for any upconversion-pumped fiber laser reported to date. Also, the noise and threshold-pumping power properties of the diode-pumped fiber laser are superior to those for its dye-laser-pumped counterpart. The highest laser slope efficiency (>22% with respect to launched pump power) was measured for a 3-μm core-diameter fiber and a cavity output coupling of 24%. The spectral interval over which the launched threshold pump power for this laser is <10 mW is almost 20 nm (637-656 nm). Studies of the fiber laser waveform as a function of pump power reveal competition for population between the ⁵S² and ⁵F₄ states and among the Stark sublevels of the ⁵F₄ manifold. Also, measurements of the output power on individual laser lines of the ⁵F₄, ⁵S₂→ ⁵I₈ (ground) transitions of Ho³⁺:ZBLAN as a function of pump power demonstrate the existence of a loss mechanism at the fiber laser wavelength, presumably due to absorption from ground or the ⁵I_y, ⁶S₂ or ⁵F₄ excited states of the ion     

Frequency measurements of 9- and 10-μm N2O lasertransitions

We have measured frequencies of N₂O transitions by heterodyning sub-Doppler fluorescence-stabilized N₂O laser radiation with that from a reference CO₂ laser. A high-resolution cavity incorporates a ribbed tube and a highly reflective grating, permitting the CW oscillation of both the 10⁰ 0-02⁰0 9-μm and the 10⁰0-00⁰1 10-μm regular bands. This is the first sub-Doppler frequency measurement of the 9-μm band. The accuracy in the determination of the rotational constants for both bands has been improved by an order of magnitude, and calculated transition frequencies are presented     

Modelocking of interferometric Y-lasers in an external cavity

The first report on active modelocking of interferometric Y-lasers in an external cavity are reported. Pulse widths between 20 and 30 ps for 1.3-μm and 1.55-μm devices were achieved by modulation of the injection current synchronously to the external cavity roundtrip frequency. A time-bandwidth-product of 0.97 was determined for 1.55-μm devices