The direct epitaxial growth of III-V semiconductor lasers on standard,
CMOS-compatible, on-axis (001) Si substrates is actively sought for
the realization of active photonic integrated circuits. Here we report
on the first mid-infrared semiconductor laser epitaxially grown on
on-axis Si substrates, i.e., compatible with industry standards.
Furthermore, these GaSb-based laser diodes demonstrate low threshold
current density, low optical losses, high temperature operation, and
high characteristic temperatures. These results represent a
breakthrough toward the integration of semiconductor laser sources on
Si for smart sensors.
Abstract:We present the design of mid-infrared and THz quantum cascade laser cavities formed from planar photonic crystals with a complete in-plane photonic bandgap. The design is based on a honeycomb lattice, and achieves a full in-plane photonic gap for transverse-magnetic polarized light while preserving a connected pattern for efficient electrical injection. Candidate defects modes for lasing are identified. This lattice is then used as a model system to demonstrate a novel effect: under certain conditionsthat are typically satisfied in the THz range -a complete photonic gap can be obtained by the sole patterning of the top metal contact. This possibility greatly reduces the required fabrication complexity and avoids potential damage of the semiconductor active region. 328-332 (1993). 15. A similar phenomenon occurs in guided membrane PC structures, where it is known that the extent of the photonic gap depends on the membrane thickness. However, in the dielectric membrane structures, beyond a critical membrane thickness further reduction in thickness does not increase the bandgap due to a loss of mode localization in the dielectric membrane. The double-metal waveguide structure does not suffer from such a loss of confinement. 1957-1964 (2006
We demonstrate the high temperature operation, up to 80°C, of quantum cascade lasers emitting at a wavelength of 20 µm. The lasers are based on the InAs/AlSb materials and take benefit of a low loss plasmon-enhanced dielectric waveguide. The waveguide consists of doped InAs cladding layers and low-doped InAs spacers. For 2.9-mm-long devices, the threshold current density is 4.3 kA/cm2 and the measured peak output power is 7 mW at room temperature. The cavity length dependence of the threshold currents also indicates that very large optical gain is achieved and effectively overcome the strong free carrier absorption.
We report low threshold InAs/AlSb quantum cascade lasers emitting near 15 µm. The devices are based on a vertical design similar to those employed previously in far infrared InAs-based QCLs, whereas the doping level of the active core is considerably decreased. The lasers exhibit a threshold current density as low as 730 A/cm2 in pulsed mode at room temperature and can operate in this regime up to 410K. The continuous wave regime of operation has been achieved in these devices at temperatures up to 20°C. The cw regime is demonstrated for InAs-based QCLs for the first time at room temperature.
We report the pulsed, room-temperature operation of λ≈7.5μm quantum cascade lasers (QCLs) in which the optical mode is a surface-plasmon polariton excitation. Previously reported devices based on this concept operate at cryogenic temperatures only. The use of a silver-based electrical contact with reduced optical losses at the QCL emission wavelength allows a reduction of the laser threshold current by a factor of 2 relative to samples with a gold-based contact layer. As a consequence, the devices exhibit room-temperature operation with threshold current densities ∼6.3kA∕cm2. These devices could be used as all-electrical surface-plasmon generators at midinfrared wavelengths.
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