A. Napoleone

Widely tunable single-mode quantum cascade laser source for mid-infrared spectroscopy

We demonstrate a compact, single-mode quantum cascade laser source continuously tunable between 8.7 and 9.4μm. The source consists of an array of single-mode distributed feedback quantum cascade lasers with closely spaced emission wavelengths fabricated monolithically on a single chip and driven by a microelectronic controller. Our source is suitable for a variety of chemical sensing applications. Here, we use it to perform absorption spectroscopy of fluids.

InGaAsP/InP avalanche photodiodes for photon counting at 1.06 μm

Geiger-mode (photon-counting) operation at 1.06 μm has been demonstrated with InGaAsP/InP avalanche photodiodes operated at room temperature. A photon detection efficiency of 33% was measured on uncoated detectors, representing an internal avalanche probability of 60%. Under identical bias conditions a dark count rate as low as 1.7 MHz was measured at 290 K, consistent with a primary dark current of <0.3 pA. Dark count rates drop by approximately 50–200× by cooling the detectors to 210 K (−63 °C).

40-Gbit/s all-optical circulating shift register with an inverter.

We report what is believed to be the first demonstration of an all-optical circulating shift register using an ultrafast nonlinear interferometer with a polarization-insensitive semiconductor optical amplifier as the nonlinear switching element. The device operates at 40 Gbits/s, to our knowledge the highest speed demonstrated to date. Also, the demonstration proves the cascadability of the ultrafast nonlinear interferometric switch.

Afterpulsing in Geiger-mode avalanche photodiodes for 1.06μm wavelength

We consider the phenomenon of afterpulsing in avalanche photodiodes (APDs) operating in gated and free-running Geiger mode. An operational model of afterpulsing and other noise characteristics of APDs predicts the noise behavior observed in the free-running mode. We also use gated-mode data to investigate possible sources of afterpulsing in these devices. For 30-μm-diam, 1.06-μm-wavelength InGaAsP∕InP APDs operated at 290K and 4V overbias, we obtained a dominant trap lifetime of τd=0.32μs, a trap energy of 0.11eV, and a baseline dark count rate 245kHz.

Slab-coupled 1.3-μm semiconductor laser with single-spatial large-diameter mode

A high brightness semiconductor diode laser structure, which utilizes a slab-coupled optical waveguide region to achieve several potentially important advances in performance, is proposed and experimentally demonstrated using a simple rib waveguide in an InGaAsP-InP quantum-well structure operating at 1.3-/spl mu/m wavelength. These lasers operate in a large low-aspect-ratio lowest-order spatial mode, which can be butt coupled to a single-mode fiber with high coupling efficiency.

High-Quality 150 mm InP-to-Silicon Epitaxial Transfer for Silicon Photonic Integrated Circuits

The integration of dissimilar materials is of great interest to enable silicon photonics and enable optical interconnects in future microprocessors. The wavelength transparency of Si in the telecom window 1.3–1.6 m is another compelling reason to integrate microphotonics and microelectronics. A major challenge for this integration is the incompatibility of the III–V compound and Si semiconductors used to implement microphotonics and microelectronics, respectively. Si and InP have an 8.1% lattice mismatch, making heteroepitaxial growth of InGaAsP compounds on Si with low misfit dislocation density difficult. 1

1.5-μm tapered-gain-region lasers with high-CW output powers

High-power diode lasers consisting of a a tapered region have waveguide section coupled to fabricated in 1.5-/spl mu/m InGaAsP-InP multiple-quantum-well material. Self-focusing at high current densities and high intensity input into the taper section has been identified as a fundamental problem in these devices that has to be dealt with. To date, continuous-wave output powers of >1 W with /spl ap/80% of the power in the near-diffraction-limited central lobe of the far field have been obtained through a judicious choice of device parameters.

High-Power, Low-Noise 1.5-μm Slab-Coupled Optical Waveguide (SCOW) Emitters: Physics, Devices, and Applications

We review the development of a new class of high-power, edge-emitting, semiconductor optical gain medium based on the slab-coupled optical waveguide (SCOW) concept. We restrict the scope to InP-based devices incorporating either InGaAsP or InGaAlAs quantum-well active regions and operating in the 1.5-μm-wavelength region. Key properties of the SCOW gain medium include large transverse optical mode dimensions (>;5 × 5 μm), ultralow optical confinement factor (Γ ~ 0.25-1%), and small internal loss coefficient (αi ~ 0.5 cm-1). These properties have enabled the realization of 1) packaged Watt-class semiconductor optical amplifiers (SOAs) having low-noise figure (4-5 dB), 2) monolithic passively mode-locked lasers generating 0.25-W average output power, 3) external-cavity fiber-ring actively mode-locked lasers exhibiting residual timing jitter of <;10 fs (1Hz to Nyquist), and 4) single-frequency external-cavity lasers producing 0.37-W output power with Gaussian (Lorentzian) linewidth of 35 kHz (1.75 kHz) and relative intensity noise (RIN) <; -160 dB/Hz from 200 kHz to 10 GHz. We provide an overview the SCOW design principles, describe simulation results that quantify the performance limitations due to confinement factor, linear optical loss mechanisms, and nonlinear two-photon absorption (TPA) loss, and review the SCOW devices that have been demonstrated and applications that these devices are expected to enable.

Diffraction-limited 1.3-μm-wavelength tapered-gain-region lasers with >1-W CW output power

Diode lasers have been fabricated in InGaAsP-InP multiple-quantum-well material grown by atmospheric-pressure organometallic vapor-phase epitaxy with an active optical cavity consisting of a ridge-waveguide region coupled to a tapered gain region. Over 1 W of CW output power was obtained with 85% of the power in the central lobe of a diffraction-limited far-field radiation pattern.

Uni-traveling-carrier variable confinement waveguide photodiodes

Uni-traveling-carrier waveguide photodiodes (PDs) with a variable optical confinement mode size transformer are demonstrated. The optical mode is large at the input for minimal front-end saturation and the mode transforms as the light propagates so that the absorption profile is optimized for both high-power and high-speed performance. Two differently designed PDs are presented. PD A demonstrates a 3-dB bandwidth of 12.6 GHz, and saturation currents of 40 mA at 1 GHz and 34 mA at 10 GHz. PD B demonstrates a 3-dB bandwidth of 2.5 GHz, a saturation current greater than 100 mA at 1 GHz, a peak RF output power of + 19 dBm, and a third-order output intercept point of 29.1 dBm at a photocurrent of 60 mA.