Surface emitting-type lasers have advanced a variety of research and development in response to the application expansion. This special issue is discussed progress, current status and future of the surface emitting-type semiconductor lasers.

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A vertical cavity surface emitting laser (VCSEL) was born in Japan. The 38 years’ research and developments opened up various applications including datacom, sensors, optical interconnects, spectroscopy, optical storages, printers, laser displays, laser radar, atomic clock and high power sources. A lot of unique features have been already proven, such as low power consumption, a wafer level testing and so on. The market of VCSELs has been growing up rapidly and they are now key devices in local area networks, and optical interconnections in data centers and supercomputers. In this paper, the advances on VCSEL photonics will be reviewed. We present the high-speed modulation of VCSELs based on a coupled cavity structure. For further increase in transmission capacity per fiber, the wavelength engineering of VCSEL arrays is discussed, which includes the wavelength stabilization and wavelength tuning based on a micro-machined cantilever structure. We also address a lateral integration platform and new functions, including high-resolution beam scanner, vortex beam creation and largeport free space wavelength selective switch with a Bragg refl ector waveguide.

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We report the low-power dissipation 1060-nm VCSELs operating at a high modulation speed of 25 Gb/s or more. We achieved a direct modulation capability of 25 Gb/s with low-power dissipation less than 125 fJ/bit. We also successfully demonstrated 28 Gb/s error-free signal transmission at a long distance of 500 m using an MMF with a modal bandwidth maximized at 1060 nm. An accelerated aging test shows the high reliability of a VCSEL that has an estimated failure rate less than 70 FIT/ch. The 1060-nm VCSEL is a promising light source for future green data centers and high performance computer systems.

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High speed ( 10 Gbps) and low power consumption 850 nm VCSEL would be one of key transmitters for optical interconnections and networks in consumer electronic devices in near future. In this report, we investigated lasing characteristics of 850 nm InGaAs strained QW VCSELs with different In composition for 10 Gbps data transmission to realize lower power consumption than that of traditional GaAs QW VCSELs that is commercially available. Low dissipated energy per bit of 43 fJ/bit for 10 Gbps modulation was achieved.

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This paper overviews the current status of polarization bistable VCSELs and their applications to alloptical signal processing. We measured the bit error rate (BER) of flip-flop operations and obtained a good BER value of 1.56 × 10‒10. We also measured the BER of flip-flop operations with AND gate functionality. From the BER variation for the set pulse power, we found that fluctuations of the switching threshold and the phase at the combination of the data and the set pulses affected BER. We demonstrated all-optical 2-bit recognition and packet switching using two 1.55-μm polarization bistable VCSELs. Optical packets including 40-Gb/s NRZ pseudo-random bit-sequence payloads were successfully switched to the one of four designated ports, depending on the state of the two bits in the headers with 4-bit 500-Mb/s RZ format. We also report a high-index-contrast subwavelength grating VCSEL (HCG-VCSEL) that incorporates a polarization-independent HCG coupled with two orthogonal in-plane output waveguides.

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I will review recent progress in high power, single mode, photonic-crystal surface-emitting lasers based on photonic band-edge effect is described. After explaining principle of device operation and the ability of generating unique beam patterns, I will describe that watt-class high-power, high-beam-quality, surface-emitting, lasing oscillation has been successfully achieved. These results represent an important milestone for innovation in the field of lasers because it provides a route towards overcoming limitations in applications that suffer from low beam quality, which opens the door to a wide range of applications in material processing, laser medicine, nonlinear optics, sensing and so on.

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A lens-integrated surface-emitting DFB laser (LISEL) array̶ for next-generation small-size and lowcost optical modules̶ has been developed. Utilizing a short-cavity DFB structure with a high-gain InGaAlAs active layer, the LISEL array achieved high-speed operation up to 40 Gbps at hightemperature. Monolithically integrating a lens on the LISEL array produces a very narrow emission beam (2.6° × 2.2°); as a result, the LISEL array demonstrated large-tolerance optical coupling to an SMF array. These results indicate that the LISEL array is a promising light source for next-generation compact and low-cost optical modules.

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We report an analytic model based on one-dimensional cantilever structure for designing the athermal and tunable MEMS VCSEL. The theoretical results calculated by using the model show good agreement with experimental results. We also discuss the theoretical limit of the wavelength tuning range with athermal operation. It is revealed that the limiting factor of the tuning range is the free-spectral-range of the cavity, which can be expanded by making the cavity length shorter.

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The operating temperature range expansion of the vertical cavity surface emitting semiconductor lasers (VCSELs) was investigated by the optical gain spectral broadening method applying the excitation quantized level of the quantum well. From the design of the quantum well structure using the excitation level, the well width of 11‒13 nm is appropriate in AlGaAs/GaAs system. Two types of VCSELs using the excitation level were fabricated based on the numerical design. The operation temperature range difference of Δ T = 269℃ and 275℃ were observed by a low temperature range design and a high temperature range design devices, respectively.

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