Surface-emitting Laser Arrays Research Articles

Photoluminescence from InGaAs/GaAs quantum well regrown on a buried patterned oxidized AlAs layer

We present a quasi-planar technological approach for forming a flexible and versatile confinement scheme based on oxidation of AlGaAs buried layers combined to an epitaxial regrowth. This method improves the electrical and optical confinements compared to the lateral oxidation since it allows to define confinement areas from a planar surface. This technique is suitable for the realization of advanced integrated photonic components arrays with close device-to-device spacing such as two-dimensional arrays of vertical-cavity surface-emitting lasers. Our results prove that the oxidation and epitaxial regrowth can be sequenced in a process flow, leading to viable confinement while preserving good radiative properties.

The 120Gbps VCSEL Array Based Optical Transmitter (ATx) development for the High-Luminosity LHC (HL-LHC) experiments

The integration of a Verticle Cavity Surface-Emitting Laser (VCSEL) array and a driving Application-Specific Integrated Circuit (ASIC) in a custom optical array transmitter module (ATx) for operation in the detector front-end is constructed, assembled and tested. The ATx provides 12 parallel channels with each channel operating at 10 Gbps. The optical transmitter eye diagram passes the eye mask and the bit-error rate (BER) less than 10−12 transmission is achieved at 10 Gbps/ch. The overall insertion loss including the radiation induced attenuation is sufficiently low to meet the proposed link budget requirement.

Self-mixing sensing system based on uncooled vertical-cavity surface-emitting laser array: linking multichannel operation and enhanced performance

We compare the performance of a self-mixing (SM) sensing system based on an uncooled monolithic array of 24×1 vertical-cavity surface-emitting lasers (VCSELs) in two modes of operation: single active channel and the concurrent multichannel operation. We find that the signal-to-noise ratio of individual SM sensors in a VCSEL array is markedly improved by multichannel operation, as a consequence of the increased operational temperature of the sensors. The performance improvement can be further increased by manufacturing VCSEL arrays with smaller pitch. This has the potential to produce an imaging system with high spatial and temporal resolutions that can be operated without temperature stabilization.

Single-Mode Vertical-Cavity Surface-Emitting Laser Array With High Power and Narrow Far-Field Divergence Angle

We demonstrate novel structures of an 850-nm vertical-cavity surface-emitting laser (VCSEL) array for high output power, single-lobe far-field pattern, and narrow divergence angle. By using the Zn-diffusion process with proper sizes of oxide-current-confined and Zn-diffusion apertures, each unit of VCSEL in the demonstrated array is highly single-mode (side-mode suppression ratio 30 dB) with a narrow far-field divergence angle (9°- 10°) and high maximum single-mode output power ( ~ 6.3 mW). Due to the high uniformity of single-mode performance of each VCSEL unit, the 6 × 6 array exhibits an excellent lasing phenomenon, which includes single-lobe far-field pattern, weak in-phase coupling, narrowing of divergence angle (from 9° to 4°), and output power as high as around 104 mW. Furthermore, by measuring the bias-dependent output optical spectra in different positions of our array, the high similarity of these spectra indicates the excellent uniformity of our fabrication process for single-mode VCSEL.

Beam steering via resonance detuning in coherently coupled vertical cavity laser arrays

Coherently coupled vertical-cavity surface-emitting laser arrays offer unique advantages for nonmechanical beam steering applications. We have applied dynamic coupled mode theory to show that the observed temporal phase shift between vertical-cavity surface-emitting array elements is caused by the detuning of their resonant wavelengths. Hence, a complete theoretical connection between the differential current injection into array elements and the beam steering direction has been established. It is found to be a fundamentally unique beam-steering mechanism with distinct advantages in efficiency, compactness, speed, and phase-sensitivity to current.

In‐phase antiguided bottom‐emitting vertical cavity laser arrays

In-phase emission from a bottom-emitting, coherently coupled, vertical cavity surface-emitting laser array is demonstrated for the first time. Various array geometries are examined. An antiguided index profile is used to obtain the preferred on-axis far-field peak from a 2 × 1 array up to 0.9 mW, representing a critical step towards coherent, high-brightness two-dimensional laser arrays.

Monolithically integrated two-dimensional arrays of surface-emitting photonic-crystal terahertz lasers

We demonstrate two-dimensional arrays of surface-emitting THz frequency photonic-crystal quantum cascade lasers covering a broad spectral range. The arrays are made of 16 unit elements, each of them spectrally single mode and featuring a narrow divergence emission pattern. The array emission frequencies cover a range of ≈0.2 THz around an emission frequency of ≈2.75 THz. Large size and small size devices have been developed. The former devices operate up to a maximum temperature of ≈90K with 2 to 3 mW output power in continuous wave regime.

Influence of optical losses on the dynamic characteristics of linear arrays of near-infrared vertical-cavity surface-emitting lasers

The effect of the level of internal and external optical losses on the dynamic characteristics of vertical-cavity surface-emitting lasers (VCSELs) in the spectral region of 850 nm is studied. It is shown that an increase in optical losses leads to a decrease in the speed of laser response and to the predominance of thermal effects, while a decrease in losses for the output of radiation brings about an increase in the response speed of the laser and the dominance of damping of the effective modulation frequency. Linear matrix emitters with the 1 × 4 format based on fast-response VCSEL with individual element addressing are produced and studied. Individual laser emitters with a current-aperture diameter of 5–7 μm provide lasing in the continuous-wave mode at room temperature in the region of 850 nm with threshold currents no higher than 0.5 mA, a differential efficiency no lower than 0.6 W/A, a modulation frequency as high as 20 GHz, and a MCEF factor of ∼10 GHz/mA1/2.

III-V-on-Si Photonic Crystal Vertical-Cavity Surface-Emitting Laser Arrays for Wavelength Division Multiplexing

Double photonic crystal mirror vertical-cavity surface-emitting laser (PCM-VCSEL) arrays for the heterogeneous integration on a complementary metal-oxide semiconductor are presented. The trimming of one-dimensional photonic crystal mirrors spectral and modal features allows a fine tailoring of the lightwave which results in compact VCSEL arrays exhibiting a fully controllable dense wavelength distribution. Optically pumped double PCM-VCSELs emit 1.55-μm single-mode beams within the C-band with sub-milliwatt thresholds and spectral purity, making these devices highly suitable for telecommunication-oriented applications. The intrinsic capability exhibited by PCM-VCSEL arrays for a selective addressing of dense wavelength division multiplexing (DWDM) channels suggests a strong perspective potential for several applications such as high-capacity ultra-wideband optical interconnects, passive optical networks, free-space data transmission and sensing.

Monolithically Lens-Integrated Photonic Device Arrays for Compact Optical Transceivers

Monolithically lens-integrated surface-emitting distributed-feedback (DFB) laser arrays and p–i–n photodiode arrays were developed. A combination of dry etching and wet chemical etching was used to fabricate a monolithic InP lens. The lens profile within ±10 µm from the lens center was estimated to be parabolic shape, which is ideal for the collimation of a Gaussian beam. A fabricated lens-integrated surface-emitting DFB laser exhibited a circular, narrow far-field pattern with full-width at half maximums of 3.9×3.5°. An efficient direct coupling of the lens-integrated DFB laser to a single-mode fiber with a coupling efficiency of -3 dB was confirmed. A four-channel lens-integrated surface-emitting laser array and a lens-integrated p–i–n photodiode array were used to fabricate a very compact 100 Gbps (25 Gbps × 4 channel) optical transceiver with 14×9 mm2 footprint.

Miniaturized bidirectional optical subassembly using silicon optical bench with 45-deg micro-reflectors in short-reach 40-Gbit/s optical interconnects

The development of a 4-channel×10-Gbits/s optical interconnect module based on a silicon optical bench (SiOB) is presented. The 4-channel vertical-cavity surface-emitting laser (VCSEL) and photo diode (PD) arrays are flip-chip assembled onto the pedestals of SiOB using Au/Sn solder bumps to form an SiOB-based bi-directional optical sub-assembly (BOSA) configuration. The optical coupling of VCSEL-to-multi-mode fiber (MMF) and MMF-to-PD without adding coupled optics is -5.2 and -2 dB , respectively. The wide alignment tolerances of 1-dB power variation for the transmitting and receiver parts to be ± 15 μ m are achieved. The clearly open 10-Gbits/s eye patterns of transmitting part as well as the 10 -12 -order bit error rate (BER) at the receiving part verify the proposed SiOB-based module is suitable for the application of 4-channel×10-Gbits/s optical interconnects.

VCSEL-Based Light Sources—Scalability Challenges for VCSEL-Based Multi-100- Gb/s Systems

Future high-performance computers require optical interconnects with aggregated Exa-Byte/s data transport. Densely packed arrays of vertical-cavity surface-emitting lasers (VCSELs) might present the only feasible technical solution. The high-speed properties of semiconductor lasers, however, are strongly affected by their operating temperature. Thermal crosstalk becomes dominant when densely packed arrays of high-speed VCSELs are required. In this paper, we derive the maximum bandwidth of future VCSEL-based optical interconnects from the influence of device heating occurring in high-speed VCSEL arrays. Furthermore, we estimate the scalability of this technology and address the challenges. From our calculations we obtain, that VCSEL arrays are scalable from a bandwidth density of 100 Gbps/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with today's devices up to a technological limit of 15 Tbps/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Optical components and optical systems for VCSEL diode laser systems

Abstract High power vertical-cavity surface-emitting laser (VCSEL) arrays can be used as a versatile illumination and heating source. They are widely scalable in power and offer a robust and economic solution for many new applications with moderate brightness requirements. The use of VCSEL arrays for high power laser diode applications enables multiple benefits: full wafer level production of VCSELs including combination with micro-optics; assembly technologies allowing large synergy with LED assembly thus profiting from the fast development in solid state lighting; outstanding reliability and a modular approach on all levels. With the use of μ-lenses, the described optical principle of near field imaging and superpositioning of many thousands of VCSELs gives perfect control over intensity distribution and is inherently robust. With a slightly modified approach, lines of any desired length can be built from modules of 1-cm length and are therefore scalable for a wide range of applications.

Phase and coherence extraction from a phased vertical cavity laser array

The relative coherence and phase are extracted from two-element, coherently coupled, vertical cavity surface emitting laser arrays. The array elements are defined optically by a photonic crystal pattern and electrically by ion implantation. We obtain the near and far fields experimentally under varying current injection. The Fraunhofer approximation is used to simulate propagation from the near to far field. The phase and coherence are extracted as fitting parameters to match the experimental and propagated far field patterns. The phase and coherence will aid in future array designs and in elucidating the phase-shifting mechanism.

Demonstration of a 5 Gb/s × 24 interchip optical interconnect system

AbstractAn 850 nm 12‐channel vertical cavity surface emitting laser array, a photodiode array, microprocessor chips, embedded fiber‐optic waveguides, and microlens optical coupling elements are integrated onto the printed circuit board. The bidirectional 5 Gb/s × 24 optical interconnect system is successfully demonstrated for interprocessor communication through optical I/O pins. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1176–1179, 2012

End-to-End Multicore Multimode Fiber Optic Link Operating up to 120 Gb/s

A full multicore fiber optic link is demonstrated, transmitting greater than 100 Gb/s through a single strand of multimode fiber for the first time. The fiber, which consists of seven graded-index multimode cores, is used to transmit up to 120 Gb/s over 100 m using a custom multicore-fiber interfacing transmitter and receiver. 2-D arrays of vertical-cavity surface-emitting lasers (VCSELs) and vertically illuminated photodiodes (PDs) are fabricated with a geometry corresponding to the outer six cores of the seven-core fiber, which is arranged in a hexagonal pattern. Both flip-chip and wire-bonding technologies are used to package the VCSEL and PD chips with multichannel transmitter and receiver integrated circuits. Amplitude and timing margins of the end-to-end signals are analyzed through bit-error-rate (BER) measurements. The effects of electrical and optical crosstalk are shown to result in negligible degradation to the BER performance.

Terabit/s-Class Optical PCB Links Incorporating 360-Gb/s Bidirectional 850 nm Parallel Optical Transceivers

We report here on the design, fabrication, and characterization of highly integrated parallel optical transceivers designed for Tb/s-class module-to-module data transfer through polymer waveguides integrated into optical printed circuit boards (o-PCBs). The parallel optical transceiver is based on a through-silicon-via silicon carrier as the platform for integration of 24-channel vertical cavity surface-emitting laser and photodiode arrays with CMOS ICs. The Si carrier also includes optical vias (holes) for optical access to conventional surface-emitting 850 nm optoelectronic devices. The 48-channel 3-D transceiver optochips are flip-chip soldered to organic carriers to form transceiver optomodules. Fully functional optomodules with 24 transmitter + 24 receiver channels were assembled and characterized with transmitters operating up to 20 Gb/s/ch and receivers up to 15 Gb/s/ch. At 15 Gb/s, the 48-channel optomodules provide a bidirectional aggregate bandwidth of 360 Gb/s. In addition, o-PCBs have been developed using a 48-channel flex waveguide assembly attached to FR4 electronic boards. Incorporation of waveguide turning mirrors and lens arrays facilitates optical coupling to/from the o-PCB. Assembly of optomodules to the o-PCB using a ball grid array process provides both electrical and optical interconnections. An initial demonstration of the full module-to-module optical link achieved >; 20 bidirectional links at 10 Gb/s. At 15 Gb/s, operation at a bit error ratio of <; 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">- 12</sup> was demonstrated for 15 channels in each direction, realizing a record o-PCB link with a 225 Gb/s bidirectional aggregate data rate.

大功率垂直腔面发射激光器列阵的热模拟及优化

大功率垂直腔面发射激光器列阵的热模拟及优化

25-Gb/s Multichannel 1.3-$\mu$m Surface-Emitting Lens-Integrated DFB Laser Arrays

Two multichannel 1.3-μ m lens integrated surface-emitting laser arrays for massive data links were fabricated. The basic structure of the lasers consists of a short InGaAlAs multiple-quantum-well distributed-feedback (DFB) active-stripe array monolithically integrated with both a 45° total reflection mirror and an aspheric collimation lens. One of them, a four-channel laser array based on this structure, exhibited clear 25-Gb/s eye openings up to 50°C over all four channels and achieved a total output of 100 Gb/s. The other laser, a multiple-wavelength array for wavelength-division-multiplexing applications, produces multiple-wavelength emission thanks to precisely modified DFB gratings by electron beam lithography. It exhibited nine-wavelength stable single-mode operation (side-mode suppression ratio >; 40 dB) between 1260 and 1290 nm at 3.7-nm intervals, and a clear 25-Gb/s eye opening for each wavelength. These two surface-emitting laser arrays have demonstrated their suitability for next-generation multichannel data links (including 100-Gb Ethernet and optical interconnects).

Two-Axis MEMS Lens Alignment System for Free-Space Optical Interconnect

We present a two-axis microelectromechanical systems (MEMS) lens aligner with a 260 μm × 220 μm translation range that positions a 6.35 mm lens with focal length f = 12.1 mm for alignment compensation of free-space optical interconnects (FSOIs) between computer servers separated by 50 mm spacing. Efficient ultrasonic linear piezoelectric motors (PMs) provide actuation with zero power required to hold the lens alignment. A four-channel FSOI is demonstrated with 1 × 4 vertical cavity surface-emitting laser (VCSEL) and photodiode (PD) arrays capable of 10 Gb/s transmission bandwidth. Demonstrated minimum step size of 1.68 μm is sufficient for aligning the 20 μm VCSEL spots onto the 40 μ m PD receivers. Force transmission between PMs and a silicon MEMS flexure stage is accomplished using a 1-mm steel ball bearing in a magnetic groove, providing compliance in the nondriven axis. The ball-coupling design has 15 μm backlash and induces a maximum of 8 μm of cross-axis motion.