GaAs Vertical-cavity Surface-emitting Laser Research Articles

Effect of a highly doped emitting window for increasing output power of 860-nm GaAs VCSELs

A highly doped emitting window for a vertical-cavity surface-emitting laser (VCSEL) was fabricated and its effect on the output power at a wavelength of 860-nm was investigated. The highly doped emitting window, which limited in required specific area, could be obtained by using various thermal conditions for patterned zinc oxide (ZnO). Experimental measurements showed that the highest doping concentration of 1.02 × 1019/cm3 was observed from patterned ZnO treated at 600 °C. The highly doped emitting window obtained by Zn diffusion effectively improved the real emission region confined by the current window owing to increase in the central concentration of the current injected from the top electrode. Among the developed VCSEL chips, the highest output power of 110 mW was observed with the use of a Zn-doped emitting widow at 600 °C, indicating an increase 47% compared with the output power of conventional chips (75 mW). For temperatures other than 600 °C, a relatively lower output power was obtained. The results show that the use of an emitting window highly doped with Zn can improve the output power of the VCSEL at a wavelength of 860-nm. It was verified that there exists an optimal thermal condition for the zinc diffusion process for patterned ZnO film required.

Use of a rough GaP layer to improve light efficiency of 860-nm GaAs-based vertical-cavity surface-emitting laser

Abstract The effects of using a rough GaP layer to improve the light efficiency of 860-nm GaAs vertical-cavity surface-emitting laser were investigated. The light efficiency was significant increased by enlargement of current flow path caused from use of GaP layer grown on the top distributed Bragg reflector (DBR) of VCSEL. Furthermore, it was found that improved light efficiency significantly could be further increased by optimizing the surface morphology of the p-GaP layer fabricated in limited surface lighting area of VCSEL. Various surface morphologies could be obtained easily by controlling the RF power of an ICP dry etching. The highest output power of 34 mW was obtained from the VCSEL with a rough GaP layer fabricated at a RF power of 40 W introduced with BCl3 gas, showing a noticeable increase of ∼113% than a conventional one (16 mW). This result clearly insists that light efficiency of 860-nm GaAs based VCSEL could be increased effectively by using the rough GaP layer.

Optically and Electrically Pumped of Ga0.65In0.35N0.02 As0.98/GaAs Vertical-Cavity Surface-Emitting Lasers (VCSELs) for 1.3 μm Wavelength Operation

The 1.27 μm pulsed operation of an electrically and an optically pumped simple bar Ga0.65In0.35N0.02As0.98 vertical-cavity surface-emitting laser (VCSEL) is reported. VCSELs are becoming an increasingly important optical source technology for long haul fibre communication systems, and are essentially working above a threshold. The structure of the device employs 21 pairs of undoped top mirrors to provide above 99 % reflectivity, while the bottom mirrors have 24 pairs of n-doped resulting in over 99.9 % reflectivity. The device has undoped top distributed Bragg reflectors (DBRs). Therefore, problems such as those associated with the refractive index contrast and the current injection, which are common with doped DBRs in conventional VCSELs, are avoided. Their intrinsic active region consists of a 7 nm Ga0.65In0.35N0.02As0.98 quantum wells QWs that embedded in undoped GaAs. At room temperature, the device was characterised through L–V and by spectral photoluminescence PL measurements. Theoretically, a peak gain at around 1.2 dB is obtained for 1.27 μm wavelength range.

Polarization axis fluctuations in a single mode VCSEL laser at 780nm

We present a transmission method to determine the polarization axis fluctuations for VCSEL (Vertical Cavity Surface Emitting Laser). The research is focused mainly on commercial lasers operatingat 780 nm, designed forlaser spectroscopy. The angle fluctuation of the laser linear axis polarization iselaborated to be less than 150 mrad. Measurement errors of this method are studied and calculated. The measurement uncertainty is ?1,4 mrad andthis is equivalent to ? 5? of arc.Changes of the linear polarization axis depending on the laser current and temperaturearepresented. Full Text: PDF References T. Ohtoshi et al., "Dependence of optical gain on crystal orientation in surface?emitting lasers with strained quantum wells", Appl. Phys. Lett.63, 1886 (1994). CrossRef K. Tateno et al., "Growth of vertical-cavity surface-emitting laser structures on GaAs (311)B substrates by metalorganic chemical vapor deposition", Appl. Phys. Lett.70, 3395 (1997). CrossRef O. Tadanaga et al., "An 850-nm InAlGaAs strained quantum-well vertical-cavity surface-emitting laser grown on GaAs (311)B substrate with high-polarization stability", IEEE Photon. Tech. Lett.12, 942 (2000) CrossRef K. Choquette, R. Leibenguth, "Control of vertical-cavity laser polarization with anisotropic transverse cavity geometries", IEEE Photon. Tech. Lett. 6, 40 (1994) CrossRef B. Weigl et al., "High-performance oxide-confined GaAs VCSELs", IEEE J. Sel. Top.Quantum Electron. 3, 409 (1997) CrossRef P. Dowd et al., "Complete polarisation control of GaAs gain-guided top-surface emitting vertical cavity lasers", Electron. Lett. 33, 1315 (1997) CrossRef M. Grabherr et al., "Volume production of polarization controlled single-mode VCSELs", Proc. SPIE,6908, 690803 (2008) CrossRef R. Roy et al., "First-Passage-Time Distributions under the Influence of Quantum Fluctuations in a Laser", Phys. Rev. Lett.45, 1486 (1980) CrossRef J. Martin-Regalado et al., "Polarization switching in vertical-cavity surface emitting lasers observed at constant active region temperature", Appl. Phys. Lett. 70, 3350 (1997) CrossRef M. B. Willemsen et al., "Polarization Switching of a Vertical-Cavity Semiconductor Laser as a Kramers Hopping Problem", Phys. Rev. Lett. 82, 4815 (1999) CrossRef M. B. Willemsen et al., "Anatomy of a Polarization Switch of a Vertical-Cavity Semiconductor Laser", Phys. Rev. Lett. 84, 4337 (2000) CrossRef T. Mukaihara et al., "Excess intensity noise originated from polarization fluctuation in vertical-cavity surface-emitting lasers", IEEE Photon. Technol. Lett. 7, 1113 (1995) CrossRef

Polarization axis fluctuations in a single mode VCSEL laser at 780nm

We present a transmission method to determine the polarization axis fluctuations for VCSEL (Vertical Cavity Surface Emitting Laser). The research is focused mainly on commercial lasers operatingat 780 nm, designed forlaser spectroscopy. The angle fluctuation of the laser linear axis polarization iselaborated to be less than 150 mrad. Measurement errors of this method are studied and calculated. The measurement uncertainty is ?1,4 mrad andthis is equivalent to ? 5? of arc.Changes of the linear polarization axis depending on the laser current and temperaturearepresented. Full Text: PDF References T. Ohtoshi et al., "Dependence of optical gain on crystal orientation in surface?emitting lasers with strained quantum wells", Appl. Phys. Lett.63, 1886 (1994). CrossRef K. Tateno et al., "Growth of vertical-cavity surface-emitting laser structures on GaAs (311)B substrates by metalorganic chemical vapor deposition", Appl. Phys. Lett.70, 3395 (1997). CrossRef O. Tadanaga et al., "An 850-nm InAlGaAs strained quantum-well vertical-cavity surface-emitting laser grown on GaAs (311)B substrate with high-polarization stability", IEEE Photon. Tech. Lett.12, 942 (2000) CrossRef K. Choquette, R. Leibenguth, "Control of vertical-cavity laser polarization with anisotropic transverse cavity geometries", IEEE Photon. Tech. Lett. 6, 40 (1994) CrossRef B. Weigl et al., "High-performance oxide-confined GaAs VCSELs", IEEE J. Sel. Top.Quantum Electron. 3, 409 (1997) CrossRef P. Dowd et al., "Complete polarisation control of GaAs gain-guided top-surface emitting vertical cavity lasers", Electron. Lett. 33, 1315 (1997) CrossRef M. Grabherr et al., "Volume production of polarization controlled single-mode VCSELs", Proc. SPIE,6908, 690803 (2008) CrossRef R. Roy et al., "First-Passage-Time Distributions under the Influence of Quantum Fluctuations in a Laser", Phys. Rev. Lett.45, 1486 (1980) CrossRef J. Martín-Regalado et al., "Polarization switching in vertical-cavity surface emitting lasers observed at constant active region temperature", Appl. Phys. Lett. 70, 3350 (1997) CrossRef M. B. Willemsen et al., "Polarization Switching of a Vertical-Cavity Semiconductor Laser as a Kramers Hopping Problem", Phys. Rev. Lett. 82, 4815 (1999) CrossRef M. B. Willemsen et al., "Anatomy of a Polarization Switch of a Vertical-Cavity Semiconductor Laser", Phys. Rev. Lett. 84, 4337 (2000) CrossRef T. Mukaihara et al., "Excess intensity noise originated from polarization fluctuation in vertical-cavity surface-emitting lasers", IEEE Photon. Technol. Lett. 7, 1113 (1995) CrossRef

Tuning Characteristics of Monolithic MEMS VCSELs With Oxide Anti-Reflection Layer

We demonstrate a micromachined tunable vertical-cavity surface-emitting laser with a monolithically formed anti-reflection (AR) layer for highly efficient electro-thermal wavelength tuning. The AR layer is formed by the lateral oxidation of an aluminum-rich AlGaAs layer and no extra process is needed. We fabricated a micromachined GaAs vertical-cavity surface-emitting laser and measured its wavelength tuning characteristic. The measurement result shows that the oxide layer functions as an AR layer for linear and efficient tuning characteristics. A large negative temperature dependence of wavelength from -0.24 to -2.0 nm/K was demonstrated using a thermally actuated cantilever for efficient electro-thermal wavelength tuning. An electro-thermal tuning efficiency of -2.3 to -4.8 nm/mW was obtained.

Optimization of VCSEL spatiotemporal operation in MMF links for 10-gb ethernet

A complete model of the spatiotemporal behavior of multimode vertical-cavity surface-emitting lasers (VCSELs), through static and dynamic response, noise, thermal effects, and its coupling to multimode fibers (MMF) has been investigated in low-cost 10-Gb Ethernet (10-Gb E) prototype optoelectronic packages using GaAs VCSEL arrays coupled to MMF ribbons for short-distance optical links. Eye diagram simulations compared to measurements allow the analysis of critical parameters, such as launching conditions, in order to maximize the MMF bandwidth as well as VCSEL static and dynamic conditions. A new bit error rate (BER) estimation method is proposed by taking into account not only the Q-factor but random and deterministic jitter and digital pattern effects. Global system optimization is discussed for a BER less than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> for an aggregate link speed of 120 Gb/s over 300 m of a 12-fiber MMF ribbon

Characteristics of MOCVD- and MBE-grown InGa(N)As VCSELs

We report our results on InGaNAs/GaAs vertical-cavity surface-emitting lasers (VCSELs) in the 1.3 µm range. The epitaxial structures were grown on (1 0 0) GaAs substrates by metalorganic chemical vapour deposition (MOCVD) or molecular beam epitaxy (MBE). The nitrogen composition of the InGa(N)As/GaAs quantum-well (QW) active region is 0–0.02. The long-wavelength (up to 1.3 µm) room-temperature continuous-wave (RT CW) lasing operation was achieved for MBE- and MOCVD-grown VCSELs. For MOCVD-grown devices with n- and p-doped distributed Bragg reflectors (DBRs), a maximum optical output power of 0.74 mW was measured for In0.36Ga0.64N0.006As0.994/GaAs VCSELs. A very low Jth of 2.55 kA cm−2 was obtained for the InGaNAs/GaAs VCSELs. The MBE-grown devices were made with an intracavity structure. Top-emitting multi-mode 1.3 µm In0.35Ga0.65N0.02As0.98/GaAs VCSELs with 1 mW output power have been achieved under RT CW operation. A Jth of 1.52 kA cm−2 has been obtained for the MBE-grown In0.35Ga0.65N0.02As0.98/GaAs VCSELs, which is the lowest threshold current density reported. The emission characteristics of the InGaNAs/GaAs VCSELs were measured and analysed.

Single-mode 1.27μm InGaAs vertical cavity surface-emitting lasers with temperature-tolerant modulation characteristics

The dynamic performance of InGaAs∕GaAs1.27μm single-mode vertical cavity surface emitting lasers (VCSELs) is presented. In order to reach such a long wavelength, the devices utilize highly strained double-quantum wells and a large detuning between the material gain peak and cavity resonance. It is found that the large detuning improves the temperature stability of both static and modulation characteristics. A resonance frequency of 7.8–9.5 GHz and optical power of 0.30 mW in fiber was maintained throughout the investigated temperature range of 20–90 °C. The intrinsic response of the device suggests that long-wavelength InGaAs∕GaAs VCSELs have the potential to be used as low cost uncooled optical transmitters at 10Gbit∕s.

1.3 μ m InGaAs vertical-cavity surface-emitting lasers with mode filter for single mode operation

We report on the performance and analysis of 1.3μm range InGaAs∕GaAs vertical-cavity surface-emitting lasers (VCSELs) with an integrated mode filter consisting of a patterned silicon layer on the top distributer Bragg reflector. In this way, 1mW of single mode power is obtained from a device with a wavelength of 1265nm and a threshold current of 2.6mA at room temperature. An effective index model is used to extract the internal and external losses of the VCSEL structure and to predict the modal losses with and without mode filter, thereby providing a useful design tool for single mode VCSELs.

Optimisation of GaAs-based (GaIn)(NAs)//GaAs vertical-cavity surface-emitting diode lasers for high-temperature operation in 1.3-μm optical-fibre communication systems

Performance of GaAs-based (GaIn)(NAs)/GaAs vertical-cavity surface-emitting diode lasers (VCSELs) at higher temperatures for second-generation optical-fibre communication systems is examined with the aid of the comprehensive threshold fully self-consistent optical-electrical-thermal-gain model. As expected, in standard double-oxide-confined VCSELs, an increase in the active-region diameter is followed by an increase in the lowest-threshold transverse mode order, especially at higher temperatures. It has been found that reduction of a diameter of the bottom aperture may ensure fundamental LP 0 1 mode operation even at higher temperatures.

120-Gb/s VCSEL-Based Parallel-Optical Interconnect and Custom 120-Gb/s Testing Station

A 120-Gb/s optical link (12 channels at 10 Gb/s/ch for both a transmitter and a receiver) has been demonstrated. The link operated at a bit-error rate of less than 10/sup -12/ with all channels operating and with a total fiber length of 316 m, which comprises 300 m of next-generation (OM-3) multimode fiber (MMF) plus 16 m of standard-grade MMF. This is the first time that a parallel link with this bandwidth at this per-channel rate has ever been demonstrated. For the transmitter, an SiGe laser driver was combined with a GaAs vertical-cavity surface-emitting laser (VCSEL) array. For the receiver, the signal from a GaAs photodiode array was amplified by a 12-channel SiGe receiver integrated circuit. Key to the demonstration were several custom testing tools, most notably a 12-channel pattern generator. The package is very similar to the commercial parallel modules that are available today, but the per-channel bit rate is three times higher than that for the commercial modules. The new modules demonstrate the possibility of extending the parallel-optical module technology that is available today into a distance-bandwidth product regime that is unattainable for copper cables.

Hybrid Integration of GaAs-Based VCSEL Array With Amorphous Silicon Sensor

We describe an optoelectronic module incorporating a vertical-cavity surface-emitting laser (VCSEL) array with a semitransparent light monitor. The power monitor is a p-i-n amorphous silicon photodetector fabricated on glass. Sets of micromachined springs for electrical contacting are also fabricated in the same process on the same glass substrate. Hybrid packages are formed by pressing the compliant springs against individual contact pads of the GaAs VCSEL array in a flip-chip assembly process. The light sensor is aligned directly on top of the laser elements. Most of the laser light is transmitted through the sensor, yet a large dynamic range is maintained because of the sensors exceedingly low dark current.

Plasmon-enhancement of optical near-field of metal nanoaperture surface-emitting laser

We propose a double-aperture structure to enhance the optical near-field in metal nanoaperture vertical-cavity surface-emitting lasers (VCSELs). We fabricated 850 nm GaAs VCSELs with subwavelength-sized double metal apertures closed to each other. The optical near-field localized in the metal apertures is strongly enhanced by the excitation of localized plasmon around the metal apertures. The far-field power radiated from the apertures is enhanced to be 16 times larger than that from a single aperture VCSEL. The peak power density is as large as 2.5 mW/μm2 with a spot size of 260 nm. The obtained power density is even larger than that of a conventional single-mode VCSEL without nanoapertures, which is very encouraging for use in high-density data storages.

Simulation of performance characteristics of GaInNAs vertical-cavity surface-emitting lasers

An advanced three-dimensional fully self-consistent optical/electrical/thermal/gain model of a 1.3 µm (GaIn)(NAs)/GaAs vertical-cavity surface-emitting laser (VCSEL) has been applied to simulate its room-temperature (RT) continuous-wave (CW) performance characteristics and to enable its structure optimisation. Localisation of the AlxOy aperture has been found to have a decisive impact on the device RT CW lasing threshold. Orders of excited transverse modes have been discovered to be dramatically reduced (and device mode selectivity considerably improved) with a decrease in the lateral size of the laser active region. Hence, RT CW single-fundamental-mode operation becomes possible in small-active-region GaInNAs VCSELs.

Long-wavelength quantum-dot lasers on GaAs substrates: from media to device concepts

Recent progress in semiconductor quantum-dot (QD) lasers approaches qualitatively new levels, when dramatic progress in the development of the active medium already motivates search for new concepts in device and system designs. QDs, which represent coherent inclusions of narrower bandgap semiconductor in a wider gap semiconductor matrix, offer a possibility to extend the wavelength range of heterostructure lasers on GaAs substrates to 1.3 /spl mu/m and beyond and create devices with dramatically improved performance, as compared to commercial lasers on InP substrates. Low-threshold current density (100 A/cm/sup 2/), very high characteristic temperature (170 K up to 65/spl deg/C), and high differential efficiency (85%) are realized in the same device. The possibility to stack QDs (e.g., tenfold) without an increase in the threshold current density and any degradation of the other device parameters allow realization of high modal gain devices suitable for applications in 1.3-/spl mu/m short-cavity transmitters and vertical-cavity surface-emitting lasers (VCSELs). The 1.3-/spl mu/m QD GaAs VCSELs operating at 1.2-mW continuous-wave output power at 25/spl deg/C are realized, and long operation lifetime is manifested. Evolution of GaAs-based 1.3-/spl mu/m lasers offers a unique opportunity for telecom devices and systems. Single-epitaxy VCSEL vertical integration with intracavity electrooptic modulators for lasing wavelength adjustment and/or ultrahigh-frequency wavelength modulation is possible. Arrays of wavelength-tunable VCSELs and wavelength-tunable resonant-cavity photodetectors may result in a new generation of intelligent cost-efficient systems for ultrafast data links in telecom.

A new process to improve the performance of 850 nm wavelength GaAs VCSELs

In this article, we propose a new process method to improve the light output power of GaAs vertical-cavity surface-emitting lasers (VCSELs). The VCSELs with filling Al metal into the ring trench will exhibit a higher quantum efficiency and have a light output power of 1.45 times higher than those without filling Al. In addition, the trench filled with Al metal can benefit in the bonding process and behavior as a mirror to reduce the output power loss. These VCSELs show good output characteristics and high-temperature operation.

10 Gb/s data transmission with TO-packaged multimode GaAs VCSELs over 1 m long polymer waveguides for optical backplane applications

TO-packaged GaAs vertical-cavity surface-emitting lasers (VCSELs) are being investigated for high-bit-rate data transmission over 103 cm of a 250×200 μm 2 core size polymer-based optical waveguide to be employed in optical backplanes. The bit-error rates for 5 and 10 Gb/s transmission over the waveguides incorporating 45° deflection mirrors are better than 10 −12. For the first time, the measured bandwidth-length-product for a polymer-based optical backplane exceeds 10 GHz× m .

Emission dynamics and optical gain of 1.3-μm (GaIn)(NAs)/GaAs lasers

The ultrafast emission dynamics of a 1.3-/spl mu/m (GaIn)(NAs)/GaAs vertical-cavity surface-emitting laser is studied by femtosecond luminescence upconversion. We obtain a minimum peak delay of 15.5 ps and a minimum pulse width of 10.5 ps. Laser operation with picosecond emission dynamics is demonstrated over a temperature range from 30 to 388 K. The bandgap shift with temperature of (GaIn)(NAs)/GaAs is determined to be about -2.9/spl middot/10/sup -4/ eV/K, which is smaller than for GaAs. Our measurements of the optical gain provide gain spectra similar to those of commercial (GaIn)(PAs)/InP-structures at moderate densities but broaden considerably for elevated carrier densities due to the stronger carrier confinement. We compare our experimental results with gain spectra calculated from a microscopic model and confirm the predictive capability of the model. The theoretical gain spectra are used as the input for a calculation of the temperature dependence of the (GaIn)(NAs)/GaAs surface-emitter emission which results in very good agreement with experiment.

3-Gb/s data transmission with GaAs VCSELs over PCB integrated polymer waveguides

GaAs quantum-well (QW)-based vertical-cavity surface-emitting lasers (VCSELs) at 855-nm emission wavelength are investigated for intraboard polymer waveguide links. We report a 3-Gb/s pseudorandom bit sequence (PRES) nonreturn-to-zero (NRZ) data transmission over about 5-cm long printed circuit board (PCB) integrated multinode polymer waveguide arrays of two different geometries at bit-error rates (BERs) of less than 10/sup -11/.