Antti Laakso

High-Power 1.48-

An output power up to 5 W at 1.48-μm wavelength is achieved from an optically pumped semiconductor disk laser. An active region composed of an AlGaInAs/InP heterostructure grown on an InP substrate was wafer fused with an AlGaAs/GaAs Bragg reflector grown on a GaAs substrate. An intracavity diamond heatspreader bonded to the gain structure surface provides efficient heat removal from the active element. The results further validate that the wafer fusion technique offers a flexible platform for high-power disk lasers in a wide wavelength range.

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A high-power dual-wavelength AlGaInAs / GaAs laser operating in a vertical external-cavity surface emitting geometry, grown by molecular beam epitaxy, is reported. The active regions of the laser are separated by an optical long-wave-pass filter to prevent absorption of short-wavelength radiation in the long-wavelength gain area. The maximum output power achieved at 15 degrees C was 0.75 W at lambda approximately 966 nm and 1.38 W at lambda approximately 1047 nm for the pump power of 21.2 W.

m Wafer-Fused Optically Pumped Semiconductor Disk Laser

Room temperature lasing operation at 599 nm for a AlGaInP/AlInP/GaAs edge-emitting laser structure is reported. The structure was grown on GaAs substrate and pumped optically with a 532 nm Q-switched laser. The lasing threshold for a 2 mm long and 25 μm wide ridge waveguide structure was 30 mW of average pump power. The orange output beam had an optical spectral width of 1.7 nm.

Dual-wavelength generation by vertical external cavity surface-emitting laser

Multi-section distributed-feedback lasers with surface gratings have been fabricated without re-growth by employing ultraviolet nanoimprint lithography. High-frequency photon-photon resonance was exploited to extend the direct modulation bandwidth beyond the conventional limits set by the carrier-photon resonance.

Optically Pumped Edge-Emitting GaAs-Based Laser With Direct Orange Emission

The conventional distributed feedback and distributed Bragg reflector edge-emitting lasers employ buried gratings, which require two or more epitaxial growth steps. By using lateral corrugations of the ridge-waveguide as surface gratings the epitaxial overgrowth is avoided, reducing the fabrication complexity, increasing the yield and reducing the fabrication cost. The surface gratings are applicable to different materials, including Al-containing ones and can be easily integrated in complex device structures and photonic circuits. Single-contact and multiple contact edge-emitting lasers with laterally-corrugated ridge waveguide gratings have been developed both on GaAs and InP substrates with the aim to exploit the photon-photon resonance in order to extend their direct modulation bandwidth. The paper reports on the characteristics of such surface-grating-based lasers emitting both at 1.3 and 1.55 μm and presents the photon-photon resonance extended small-signal modulation bandwidth (> 20 GHz) achieved with a 1.6 mm long single-contact device under direct modulation. Similarly structured devices, with shorter lengths are expected to exceed 40 GHz small-signal modulation bandwidth under direct modulation.

Distributed feedback lasers with photon-photon-resonance-enhanced modulation bandwidth

Distributed feedback lasers with third-order surface gratings obtained by lateral corrugations of the ridge waveguide have been fabricated using low-cost nanoimprint lithography. The lasers, emitting in the 980 nm wavelength range exhibited stable single-longitudinal-mode operation with side-mode suppression ratios up to 50 dB.

Development of high-speed directly modulated DFB and DBR lasers with surface gratings

Semiconductor optical amplifiers (SOAs) are a well-established solution of optical access networks. They could prove an enabling technology for DataCom by offering extended range of active optical functionalities. However, in such costand energy-critical applications, high-integration densities increase the operational temperatures and require powerhungry external cooling. Taking a step further towards improving the cost and energy effectiveness of active optical components, we report on the development of a GaInNAs/GaAs (dilute nitride) SOA operating at 1.3μm that exhibits a gain value of 28 dB and combined with excellent temperature stability owing to the large conduction band offset between GaInNAs quantum well and GaAs barrier. Moreover, the characterization results reveal almost no gain variation around the 1320 nm region for a temperature range from 20° to 50° C. The gain recovery time attained values as short as 100 ps, allowing implementation of various signal processing functionalities at 10 Gb/s. The combined parameters are very attractive for application in photonic integrated circuits requiring uncooled operation and thus minimizing power consumption. Moreover, as a result of the insensitivity to heating issues, a higher number of active elements can be integrated on chip-scale circuitry, allowing for higher integration densities and more complex optical on-chip functions. Such component could prove essential for next generation DataCom networks.

Surface-grating-based distributed feedback lasers fabricated using nanoimprint lithography

Simulations and experimental results of high-frequency photon-photon resonance are used to examine the possibilities to extend the direct modulation bandwidth in dual-mode distributed feedback lasers beyond the conventional limit set by the carrier-photon resonance.

High gain 1.3-μm GaInNAs SOA with fast-gain dynamics and enhanced temperature stability

This paper presents state-of-the-art results concerning 1.55 μm single quantum well (QW) GaInNAsSb/GaAs ridge waveguide (RWG) laser diodes and SOAs, which are expected to outperform traditional InP-based components in temperature characteristics due to the large conduction band offset between the GaInNAsSb QW and GaAs.

Simulation of photon-photon resonance enhanced direct modulation bandwidth of DFB lasers

The epitaxial overgrowth, employed in the fabrication of conventional buried gratings, is avoided by using lateral corrugations of the ridge-waveguide as surface gratings, thus decreasing the fabrication complexity, increasing the yield and reducing the fabrication cost of distributed feedback and distributed Bragg reflector edge-emitting lasers. Single-and multiple-contact edge-emitting lasers with laterally-corrugated ridge waveguide gratings have been developed both on GaAs and InP substrates with the aim to exploit the photon-photon resonance in order to extend their direct modulation bandwidth. The characteristics of such surface-grating-based lasers emitting both at 1.3 and 1.55 µm are presented, including photon-photon-resonance-extended small-signal modulation bandwidth in excess of 20 GHz achieved with a 1.6 mm long single-contact device under direct modulation. Similarly structured devices, with shorter lengths are expected to exceed 40 GHz small-signal modulation bandwidth under direct modulation.