Ridge Waveguide Laser Diodes Research Articles

A comparative study on ridge waveguide laser diodes with SiO2 and SiNx passivation layers

AbstractIn this study, we have reported the fabrication and device characteristics of metal organic chemical vapor deposition (MOCVD) grown 1.3‐µm InP‐based InGaAsP multiquantum well ridge waveguide laser diodes (LDs) for communication systems. The LD parameters such as threshold current, differential resistivity and output power for SiO2 and SiNx passivation layers have been compared. Fabricated LDs have a threshold current, differential resistivity and output power values of 42 mA, 20 Ω, 9.3 mW and 51 mA, 25 Ω, 6.8 mW for SiO2 and SiNx passivation layers, respectively. The analyses showed that the fabricated LD with SiO2 passivation layer has a better performance than the other one in the view of lower threshold current, differential resistivity and higher output power. Copyright © 2010 John Wiley & Sons, Ltd.

High-power distributed Bragg reflector ridge-waveguide diode laser with very small spectral linewidth

We manufactured and investigated distributed Bragg reflector ridge-waveguide diode lasers having sixth-order surface gratings and an emission wavelength around 974 nm. The single-mode output power of the lasers with a total length of 4 mm exceeded 1 W. A very small spectral linewidth of 1.4 MHz (3 dB) consisting of a Lorentzian part of 146 kHz and a Gaussian part of 1308 MHz was measured using a self-delayed heterodyne measurement technique.

Low-Threshold Strained Quantum-Well GaSb-Based Lasers Emitting in the 2.5- to 2.7-$\mu$m Wavelength Range

GaInAsSb-GaSb strained quantum-well (QW) ridge waveguide diode lasers emitting in the wavelength range from 2.51 to 2.72 mum have been grown by molecular beam epitaxy. The devices show ultralow threshold current densities of 44 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> rarr infin) for a single QW device at 2.51 mum, which is the lowest reported value in continuous-wave operation near room temperature (15degC) at this wavelength. The devices have an internal loss of 3 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and a characteristic temperature of 42 K. By using broader QWs, wavelengths up to 2.72 mum could be achieved.

High-power 808 nm ridge-waveguide diode lasers with very small divergence, wavelength-stabilized by an external volume Bragg grating

We present data on ridge-waveguide diode lasers having a vertical far-field divergence of only 11.5 degrees (FWHM) owing to an appropriate waveguide design. The lasers emitted an optical power of more than 1 W into the spatial fundamental mode from a ridge width of 5 microm. The emission wavelength was stabilized to a narrow range around 808 nm by placing a volume Bragg grating in front of the outcoupling facet.

High-temperature operation of 1.26 µm Fabry-Perot laser with InGaAs metamorphic buffer on GaAs substrate

A 1.26 µm ridge waveguide laser diode with an InGaAs metamorphic buffer on a GaAs substrate grown by metal-organic vapour-phase epitaxy has been successfully developed. This laser has achieved the highest operating temperature (173°C) for continuous-wave operation reported for a metamorphic laser.

Native-oxide-confined high-index-contrast λ=1.15 μm strain-compensated InGaAs single quantum well ridge waveguide lasers

High performance native-oxide-confined high-index-contrast (HIC) ridge waveguide (RWG) diode lasers are fabricated in a strain-compensated In0.4Ga0.6As single quantum well structure by employing a deep dry etch plus nonselective O2-enhanced wet thermal oxidation process. The thermal native oxide grown on the etch-exposed RWG sidewalls of the Al0.74Ga0.26As waveguide cladding layers and GaAs core with GaAsP–InGaAs quantum well provides both strong optical and electrical confinements for the active region. Due to a smoothing of sidewall roughness by the O2-enhanced oxidation, the lasers exhibit a low internal loss in αi=7.2 cm−1 for a w=7.2 μm narrow stripe HIC RWG structure, only 53% larger than that of w=87.2 μm broad-area devices, enabling their room temperature operation at a low 300 A/cm2 threshold current density.

Modified Face-Down Bonding of Ridge-Waveguide Lasers Using Hard Solder

A modified face-down bonding technique of ridge-waveguide laser diodes (LDs) using 80Au20Sn solder has been performed. For ease of manufacturability, a bonding window with good bonding integrity and improved optical performance was determined. Metallographical investigation showed that the solder joint comprised of a layer of delta phase compound near the solder/heatsink interface, a layer of (Au,Ni)Sn intermetallic compound (IMC) at the solder/heatsink interface, and zeta' phase Au/Sn compound at the center of the solder joint. The delta phase shifted to the interfaces after reflow was postulated by its lower surface tension than zeta' phase Au/Sn compound. Good bonding integrity was observed with LD residues still adhering onto the bond pad after die shear testing. Scanning electron microscopy (SEM)/energy dispersive X-ray (EDX) analyses of the fracture surface showed that the fracture occurred within the LD, at the GaAs/SiN interface. LDs bonded with this modified bonding process achieved an optical improvement of 2.5-3X compared to the unbonded LDs due to its good thermal management. These bonded LDs further exhibited good long-term reliability with no significant degradation in optical performance and no significant microstructure evolution in the solder joint after 500 thermal cycling test.

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 µm is centred at 1337.2 nm; the threshold current density is 205 A/cm2 at room temperature under continuous-wave operation.

High-power and long-lifetime InGaN blue–violet laser diodes grown by molecular beam epitaxy

InGaN 405 nm multiple quantum well laser diodes grown by molecular beam epitaxy (MBE) with a continuous-wave (CW) lifetime of up to 42 h are reported. The CW threshold current density of the ridge waveguide laser diodes is 3.6 kA/cm2 and the slope efficiency for uncoated facets is 0.42 W/A per facet with a maximum CW output power of 45 mW per facet. Statistical variation of CW lifetime with dissipated power is presented for MBE-grown laser diodes from five different wafers.

Operational Properties of Ridge Waveguide Lasers with Laterally Tapered Waveguides for Monolithic Integration

We report on a ridge waveguide laser diode with laterally tapered waveguides fabricated in a single growing step using a double patterning method. In this structure, nearly constant output power is obtained with the change of the lower tapered waveguide width, and the facet power ratio of 1.4 to 1.5 is observed over the current range. The asymmetric facet power property is also investigated.

High-Temperature Continuous-Wave Operation of GaInAsN–GaAs Quantum-Dot Laser Diodes Beyond 1.3 $\mu$m

Internal laser parameters and characteristic temperature T0 of a GaInAsN-GaAs quantum-dot (QD) laser emitting above 1350 nm were determined. Continuous-wave operation of GaInAsN-GaAs QD ridge waveguide laser diodes with an emission wavelength of 1355 nm at room temperature (RT) is reported for the first time. Low threshold currents of 16 mA are achieved at RT. Ground state laser emission is observed up to temperatures of 75degC with a resulting laser emission wavelength of 1395 nm.

Optoelectronic Noise and Photocurrent Measurement on GaAs/AlGaAs Laser Diode with Single Quantum Well

The current progress in optomechatronic applications needs more efficient devices and components with higher reliability, operational lifetime, reduced cost, and dimensions as laser diodes, fast photodetectors, and modulators. The laser is one key technology in a highly industrialized economy. To understand modern efficient laser diode (LD) structures and evaluate their performance, an electrical and optical characterization is necessary. Therefore, low-frequency electrical and optical fluctuation spectra and their cross-correlation factor have been investigated in GaAs/AlGaAs ridge waveguide laser diode with an active region containing a single quantum well layer. It is shown that in the lasing region the intensive Lorentzian-type electrical and optical noises with negative cross-correlation factor are characteristic. This noise is due to charge carrier recombination processes in the interfaces between the active layer and the neighboring layers. To verify it, a complementary insight into the same laser diode structure provided by near-field-induced photocurrent technique with 100 nm spatial resolution is also discussed.

High-Temperature and High-Frequency Operation of 1.3 μm AlGaInAs ∕ InP Laser Diodes Using Silicon Oxide Planarization

In this article, a self-terminated oxide polish (STOP) planarization technique is utilized to fabricate high-temperature and high-speed ridge-waveguide laser diodes (LDs). The as-cleaved LDs fabricated by this STOP technique exhibit a threshold current of 8.5 and , and a light output power of 27 and at for 0 and , respectively. The characteristic temperature is from 0 to and from 80 to . The full width at half maximum of the lateral far-field angle is for the conventional ridge LDs and reduces to for the LDs by the STOP technique. The modulation bandwidth at of the LDs can reach 16.9 at and at .

Period-doubling and total mode-locking, and chaotic pulsations in a GaAs ridge wave-guide external-cavity diode laser

We report on the experimental observations of a period-doubling route to chaos and a total mode-locking between two lowest-order lateral modes of a GaAs ridge wave-guide diode laser at 795 nm. A self-starting passively mode-locking was achieved in an extended-cavity diode laser (ECDL) operating in a gain saturation regime. In the period-doubling mode-locked state, the RF spectra associated with the coherently coupled lateral TE(0) and TE(1) modes, consisted of harmonics (nf(rep)/2, n is an integer) of the half of pulse repetition rate f(rep)/2 and the period (2T) of the pulse train was two-times longer than the pulse round-trip time T. On the other hand, in the total mode-locked state, the RF spectra and the pulse train corresponding to the TE(0) and TE(1) modes had exactly the same features compared to those of the period-doubling mode-locked state, except the RF spectra and the pulse train of the TE(1) mode were shifted by f(ref)/4 in frequency and by T in time, respectively, indicating the pulses actually traveled alternatively through two lateral modes. The total mode-locking and also chaotic pulsations were observed at slightly different operation parameters, e.g. at different feedback angle of the grating, which was used as an output coupler of the ECDL.

Single-Facet Folded-Cavity Diode Laser With Ultrasmall Bend Radius High-Index-Contrast Oxidized AlGaAs Ridge Waveguide

AlGaAs heterostructure high-index-contrast (HIC) ridge waveguide (RWG) diode lasers incorporating a folded-cavity single-facet resonator with a folding bend radius as small as r=10 mum are demonstrated. Fabricated by a self-aligned deep dry etch (through the active region) plus nonselective O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -enhanced wet thermal oxidization process, the low-index, insulating, and interface-passivating wet thermal oxide grown directly on the etch-exposed AlGaAs waveguide sidewalls yields a high lateral refractive index contrast of Deltan~1.7 and provides strong optical mode confinement. The HIC RWG device geometry also completely eliminates lateral current spreading, which results in an excellent overlap between the optical field and the gain region of the single InAlGaAs quantum-well graded-index separate confinement heterostructure. A threshold current of I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> =65mA is obtained for the r=10 mum device (a half-racetrack ring resonator), giving a threshold current density of Jth=1503 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , 3.34 times higher than that of same-length straight lasers. At a bend radius of r=150 mum, I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> =16.6 mA, and J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> is comparable to straight cavity values, indicating that at this curvature there is negligible bending and scattering loss for the lowest-order waveguide mode

Deep-Etched Native-Oxide-Confined High-Index-Contrast AlGaAs Heterostructure Lasers With 1.3 $\mu$m Dilute-Nitride Quantum Wells

Using a modified, O2-enhanced nonselective wet thermal oxidation process, deep-etched ridge waveguides in AlGaAs heterostructures containing lambda = 808 nm InAlGaAs single quantum well or aluminum-free lambda = 1.3 mum GaAsP/InGaAsN dilute nitride multi-quantum-well active regions have been directly oxidized to effectively provide simultaneous electrical isolation, interface state passivation, and sidewall roughness reduction. The resulting high- index-contrast (HIC) ridge waveguide (RWG) diode lasers show improved performance relative to conventional shallow-etched devices owing to both strong optical confinement and the complete elimination of current spreading, with 5 mum stripe width dilute- nitride devices showing up to a 2.3 times threshold reduction and strong index guiding for kink-free operation. Oxidation of an AlGaAs graded-index separate confinement heterostructure is studied for varying O2 concentrations, and the interface passivation effectiveness of the native oxide is studied through comparison with deposited SiO2 and via a study of the stripe-width dependence of internal quantum efficiency and modal loss. The HIC RWG structure is shown to enable the operation of half-racetrack-ring- resonator lasers with a bend radius as small as r = 6 mum.

Characteristics of InGaN multiple quantum well blue-violet laser diodes

Studies on InGaN multiple quantum well blue-violet laser diodes have been reported. Laser structures with long-period multiple quantum wells were grown by metal-organic chemical vapor deposition. Triple-axis X-ray diffraction (TAXRD) measurements show that the multiple quantum wells were high quality. Ridge waveguide laser diodes were fabricated with cleaved facet mirrors. The laser diodes lase at room temperature under a pulsed current. A threshold current density of 3.3 kA/cm2 and a characteristic temperature T0 of 145 K were observed for the laser diode.

Gain and lifetime of GaInNAsSb narrow ridge waveguide laser diodes in continuous-wave operation at 1.56μm

The continuous-wave (cw) operation of GaInNAsSb lasers at 1560nm is reported. Light-current measurements were made before and after a 100h cw burn in at 20°C, during which a 3×890μm2 device with 72mA initial threshold current and 14mW maximum output power experienced a 15% drop in peak output power. These preliminary lifetime results provide insight into the reliability of GaInNAsSb active regions and reinforce the promise of this material for C-band devices. High-resolution modal gain spectra were extracted from the amplified spontaneous emission spectra acquired after the burn in, providing reliable values for the internal loss, transparency current, and differential gain.

Uncooled 1.3-/spl mu/m complex-coupled DFB BH laser diodes with the Fe-doped InGaAsP-InP hybrid current-blocking grating

We proposed an alternate method by using the Fe-doped InGaAsP-InP hybrid grating layers to fabricate the 1.3-μm current-blocking-grating complex-coupled distributed-feedback (CBG CC-DFB) laser diodes (LDs) grown by metal-organic chemical vapor deposition (MOCVD). By combining the Fe-doped InGaAsP-InP grating layers, the CBG CC-DFB LDs can provide high optical DFB coupling coefficient and high current confining ability. Moreover, the current aperture in the lateral direction can be easily controlled by the self-aligned MOCVD regrowth process. Therefore, the manufacture of CBG CC-DFB buried heterostructure LDs is easy as the ridge-waveguide LDs. The LDs exhibit a low threshold current of 5.3 mA, a high slope efficiency of 0.42 mW/mA, and a stable single mode with a high sidemode suppression ratio of /spl sim/42 dB at two times the threshold (10.5 mA). Even at high temperatures, these LDs still have an extremely low threshold current of 15.8 mA at 90/spl deg/ and a small variation in slope efficient of only -1 dB at the temperatures between 20/spl deg/ and 80/spl deg/. Furthermore, these LDs show a high-speed characteristic of more than 11.8 GHz at 20/spl deg/, which are suitable for 10-Gb/s Ethernet and OC-192 applications.

Low-cost and high-performance 1.3-/spl mu/m AlGaInAs-InP uncooled laser diodes

In this letter, we utilize a self-terminated oxide polish (STOP) planarization technique to fabricate high-yield, high-performance, low-cost, and uncooled 1.3-mum ridge-waveguide AlGaInAs-InP laser diodes (LDs). The STOP technique is superior to the polyimide planarization, which suffers from high-temperature sustainability. The LDs fabricated by the STOP technique exhibit threshold currents of 8.5 and 30.5 mA, and light output powers of 25.9 and 4.8 mW at 100 mA for 20degC and 110degC, respectively. The characteristic temperatures (T 0) are 82.6 K from -30degC to 80degC and 55.9 K from 80degC to 110degC. Since the metal pad lies on a thick SiO2 layer, the parasitic capacitance can be effectively lowered to 2 pF. The 3-dB modulation bandwidths of the LDs at 50 mA are 12.1 and 9.44 GHz at 20degC and 90degC, respectively