Single wavelength grating filter laser array withGa0.3In0.7As/GaInAsP/InP strained MQW structure

Stable in-phase lateral- and single-longitudinal-mode operation up to four times the threshold (P_o~100 mW) was achieved in a five-element 1.5-μm-wavelength Ga_0.3In_0.7As/GaInAsP/InP compressive strained MQW grating filter laser array. The threshold current and external differential quantum efficiency under pulsed condition were 330 mA (emitter width of 18 μm, active region length of 480 μm) and 17%, respectively     

High-power antiguided laser array fabricated without the need forovergrowth

The fabrication of conventional semiconductor antiguided laser array structures involves etching of the array profile followed by an overgrowth step. In this letter, we report the fabrication of an antiguided laser array using zinc diffusion induced intermixing of a superlattice to create the necessary index step. The technique was used to fabricate a five-element, 10-μm center, antiguided laser array operating at 0.860 μm. The device operated at 1.2× diffraction limit to 3-W pulsed (total, both facets) and 1.6-W quasi-continuous-wave (CW) (100-μs pulses; total, both facets)     

High power antiguided laser array fabricated using a superlatticestructure

The operation of antiguided array lasers is dependent on the creation of an effective refractive index step between the antiguide core and the interelement regions. The authors describe a novel technique, using zinc diffusion to disorder a superlattice, for creating the necessary index step in a 10 element antiguided laser array operating at 0.860 μm. Output powers approach 400 mW per facet into a 3° (FWHM) beam. Use of this fabrication technique removes the need for overgrowth     

Dither-free absolute frequency locking of a 1.3 μm DFB laser on87Rb

A technique for frequency locking a semiconductor laser in the 1.3 μm region by observing the absorption in a ⁸⁷Rb vapor optically pumped by another frequency-modulated semiconductor laser is presented. This technique offers well-defined strong atomic resonances and does not require frequency dithering of the 1.3 μm laser to observe the discrimination pattern required for frequency locking. Dither-free absolute frequency locking of a DFB (distributed feedback) laser at 1324 nm was achieved using a pump laser diode operating at 795 nm (D₁-line). Applications include master oscillator of multiwavelength and coherent communication systems and reference source for an optical frequency synthesizer. Resonances in the 1.55 μm region are also available through this approach     

Modal properties of two-dimensional antiguided vertical-cavitysurface-emitting laser arrays

We present a detailed analysis on 2-D (4 × 4 square-lattice) antiguided vertical-cavity surface-emitting laser (VCSEL) arrays based on the effective-index model. The calculation shows that the array can operate under 2-D resonant coupling, provided that the resonance condition in both the horizontal and vertical directions is satisfied. Consequently, the resonant-mode edge radiation loss is inversely proportional to the number of array elements along one direction for a N × N array. Low-edge-loss out-of-phase and adjacent array modes are found to compete with the in-phase resonant mode. While the 3-D gain overlap is not a significant factor in modal discrimination, the introduction of inter-element loss allows the in-phase mode to exhibit the lowest threshold gain for a wide range of inter-element width, s (Δ₈ ≈ 0.5 μm for 980-nm wavelength devices). The 2-D antiguided array results from shifting the cavity resonance between the element and inter-element regions and is fabricated by selective chemical etching and two-step metalorganic chemical vapor deposition growth. Diffraction-limited in-phase and out-of-phase array mode operation is observed from top-emitting arrays, depending on the inter-element width. Substrate-emitting array structures are investigated as a means to lower heating and increase the coherent output power     

Antiguided laser array structure at 1.48 μm fabricated withoutovergrowth

The authors describe the fabrication of five-element antiguided laser arrays at 1.48 μm using a novel material design which removes the need for overgrowth. Adding undoped passive waveguiding layers to the standard laser design significantly alters the shape of the far field emission from the lasers, showing that the array elements are pulled in phase with each other     

Diode-array pumping of Er3+/Yb3+ Co-dopedfiber lasers and amplifiers

Single-mode double-clad Er³⁺/Yb³⁺ co-doped fibers are shown to be suitable for diode array pumping at around 960 nm. A fiber laser with 96-W output power at 1.53 μm and a power amplifier exhibiting a small signal gain of 24 dB and a saturated output power of +17 dBm are reported     

Single mode multiple-element laser array with grating filter

A 1.5-μm wavelength grating filter laser array (GFA) structure which consists of a positive-index-guided multiple-element array region and a laterally unguided grating filter region is proposed and theoretically analyzed for realizing in-phase supermode and simultaneous single-longitudinal-mode operation. A five-element GaInAsP/InP GFA with a lasing wavelength of ~1.5 μm was fabricated and its single-longitudinal-mode/in-phase supermode operation was demonstrated up to four times the threshold current     

Single-mode Nd3+-doped graded-index polymer waveguideamplifier

The first graded index (GRIN) polymer waveguide amplifier working at 1.06 μm wavelength has been realized, using a Nd³⁺: photolime gel material combination. Throughput intensity of 3.8 mW at 1.06 μm, corresponding to 8.5 dB gain, was observed when employing a 40 mW pumping laser beam operating at 790 nm. The gain medium is a 2.2 cm waveguide active region with Nd³⁺ concentration of 1.03×10²⁰/cm³. The GRIN characteristic of the photolime gel thin film provides a universal means for implementing polymer-based photonic integrated circuits (PICs) on any substrate of interest     

An InGaAs/GaAs SQW laser integrated with a surface-emittingharmonic generator for DWDM applications

An In_0.22Ga_0.78As/GaAs single quantum-well (SQW) laser integrated monolithically with a surface-emitting harmonic generator (SEHG) segment was fabricated and tested. By coupling a 1.06-μm Nd:YAG laser output into the active device, the green surface-emitting light at 0.51 μm was observed as the result of nonlinear interactions within the SEHG segment. The nonlinear interaction cross section A^nl of the device was found to be 2.3×10^-7 W^-1, which agrees well with theory. The application of the active devices as a dense wavelength-division-multiplexing (DWDM) demultiplexer was demonstrated with a tunable Ti:sapphire laser to simulate the multiwavelength signal source and a CCD detector array to record the spatially separated signals of different wavelength. System resolution better than 2 nm was obtained for the device, which was limited by the short length of the SEHG segment. Potential for a DWDM channel spacing of 10 GHz is discussed     

155 W CW optical power from 1 cm monolithic AlGaAs/InGaAs laserdiode array

155 W continuous-wave output power from a 1 cm wide monolithic AlGaAs/InGaAs laser diode array with an emitting aperture of 4800 μm has been demonstrated at a cooling water temperature of 3°C. A continuous-wave output power of 72 W was achieved at room temperature with an emitting aperture of 1600 μm. High T₀ was observed for the laser structures     

10W near-diffraction-limited peak pulsed power from Al-free, 0.98μm-emitting phase-locked antiguided arrays

10 W peak-pulsed power emitted in a beam pattern 2×diffraction limit (DL) is obtained from a 40-element, 200 μm-aperture Al-free phase-locked antiguided array (λ=0.98 μm). 60% of the power resides in the central lobe, and the external differential quantum efficiency is 54%, for 1 mm-long optimised facet-coated devices     

Frequency stabilization of 1.55 μm DFB laser diode usingvibrational-rotational absorption of 13C2H2 molecules

The vibrational-rotational absorption of ¹³C₂H₂ molecules (VRAMs) in the 1.52-1.55 μm region was investigated in detail. On the basis of this investigation, frequency stabilization of 1.55-μm distributed-feedback (DFB) laser diodes was demonstrated. Frequency stability to within 2 MHz peak/peak fluctuation was achieved at the 1.54949-μm wavelength. In addition, frequency stabilizations in the wavelength regions of 1.53 μm and 1.54 μm were also carried out by using the strong absorption lines of ¹³C₂H₂ VRAM in these wavelength regions. The spectral width of the frequency-stabilized DFB laser diode was found to be 25 MHz. The absolute frequency was found to be stabilized at least to within 25 MHz by the measurement of beat spectrum     

InxGa1-xAs-AlyGa1-yAs-GaAs strained-layer quantum-well heterostructure circular ringlasers

The growth, processing, and optical characterization of a single Y-junction In_xGa_1-xAs-Al_yGa_1-y As-GaAs strained-layer quantum-well heterostructure circular ring laser (6 μm width, 11~251 μm outer radius) are described. The circular ring lasers have been grown by metalorganic chemical vapor deposition, etched by SiCl₄ reactive ion etching, and planarized by polyimide. The dependences of laser threshold current density and peak emission wavelength (950~1015 nm) on outer radius are presented. The emission spectra show that the circular ring lasers lase mainly in high-order whispering gallery modes, with smaller outer radius ring lasers operating in low-order whispering gallery modes     

Frequency stabilization of laser diodes using 1.51-1.55 μmabsorption lines of 12C2H2 and 13C2

Frequency stabilization of a 1.55 μm DFB laser diode is demonstrated using vibrational-rotational absorption of ¹²C ₂H₂ and ¹³C₂H₂ molecules (named VRAM). Frequency stability within 2 MHz peak to peak fluctuation can be achieved in the wavelength region of 1.51-1.55 μm. Frequency-stabilized DFB laser compact modules have been constructed. Frequency stabilities are evaluated by measuring the beat spectrum of the two lasers. In addition, the temperature and pressure dependences of the acetylene absorption lines are characterized     

Optical amplification in Er3+-doped single-mode fluoridefiber

The amplification characteristics at around 1.5 μm of a 0.9-m-long, 1000-p.p.m Er³⁺-doped single-mode fluoride fiber are discussed. By using 1.48-μm laser diodes with 55-mW launched output as a pump source, a gain of 1.75 dB was obtained at 1.530 μm. A broad bandwidth of 40 nm was obtained, which may be suitable for wavelength-division multiplexing (WDM) system use     

Performance analysis of a dispersion compensator usingarrayed-waveguide gratings

We have developed a dispersion compensator that uses arrayed-waveguide gratings (AWGs) and a spatial filter. The compensator using AWGs with 380 waveguides in each array and the diffraction order of 53, can compensate a total second-order dispersion of 260 ps/nm with an eye-closure penalty of 1 dB for a 40-Gb/s nonreturn-to-zero (NRZ) signal. It is shown that the required spatial resolution of the spatial phase filter for compensation is 2.55 μm for silica AWGs of usual design. The acceptable fluctuation in the refractive index of the waveguides in the AWGs is as large as 5×10^-5     

Mid-infrared fluoride fiber lasers in multiple cascade operation

CW fiber laser cascades in an Er³⁺-doped fluorozirconate fiber operating simultaneously at 2.7 μm/1.55 μm or at 3.45 μm/2.7 μm/1.55 μm pumped around 650 nm are reported. Output powers of nearly 20 mW at 1.55 μm and 1.2 mW around 2.7 μm were obtained with a nonoptimized experimental setup for the 2.7 μm/1.55 μm cascade. At 1.55 μm a laser efficiency of 5% was achieved. By varying the parameters of the experimental setup, additional effective simultaneous laser action at 3.45 μm was demonstrated     

Tunable UV generation to 0.2325 μm in LiB3O5

LiB₃O₅ has been found to be phase matchable for sum-frequency generation down to 0.2325 μm at 20.0°C by mixing the Nd:YAG laser wavelength at 1.0642 μm with the second harmonic of a visible dye laser. Sellmeier's equations, which are highly accurate from 0.22 to 1.32 μm, are reported. It is demonstrated that a much shorter wavelength of 0.218 μm could be generated in this compound by mixing the fourth harmonic of a Nd:YAG laser with the idler of the KNbO₃ parametric oscillator tuned to 1.208 μm