Clara Dimas

Micromachined Deformable Mirrors for Adaptive Optics

Recent progress on deformable mirror systems made at Boston University and Boston Micromachines Corporation is described. The mirrors optical, electrical, and mechanical performance characteristics are summarized, and the effects of air damping on performance are described. Two applications that have employed the μDM in laser communications and retinal imaging are introduced.

InGaAs/GaAs Quantum-Dot Superluminescent Diode for Optical Sensor and Imaging

We report on the design and fabrication of a novel wideband superluminescent diode (SLD) based on InGaAs/GaAs quantum-dot structure. In this device, we monolithically integrate a photon absorber section to suppress lasing action and optical feedback oscillation. The fabricated SLDs produce a close-to-Gaussian shaped spectrum centered at 1210 nm with a bandwidth of 135 nm. Spectral ripple as low as 0.3 dB has been measured

Wideband quantum-dash-in-well superluminescent diode at 1.6 /spl mu/m

We demonstrate broadband superluminescent diode at ~1.6-mum peak emission wavelength using InAs-InAlGaAs quantum-dash-in-well structure on InP substrate. The fabricated device exhibits the close-to-Gaussian emission with a bandwidth of up to 140 nm. The device produces a low spectrum ripple of 0.3dB and an integrated power of 1.7 mW with the corresponding bandwith of 110 nm measured at 20 degC under 8 kA/cm2

Wavelength tuning and emission width widening of ultrabroad quantum dash interband laser

The authors report the demonstration of the bandgap-tuned InAs quantum dash broadband laser with widened laser emission linewidth at room temperature using postgrowth intermixing technique. The 100 nm wavelength blueshifted, as-cleaved laser exhibits ultrabroad lasing spectral coverage of ∼85 nm at a center wavelength of 1.54 μm with a total emission power of ∼1 W per device. Compared to the as-grown laser, this laser shows broader lasing bandwidth (∼41 nm) with improved spectral ripple (<1 dB).

The Influence of Nonequilibrium Distribution on Room-Temperature Lasing Spectra in Quantum-Dash Lasers

We demonstrate the effect of nonequilibrium carrier distribution in a self-assembled InAs-InAlGaAs quantum-dash-in-well semiconductor lasers on InP substrate. The progressive changes of electroluminescence spectrum with increasing injections show the presence of localized photon reabsorption and lasing action from different dash ensembles at room temperature as opposed to that obtained in typical self-assembled quantum-dot lasers only at low temperature below 100 K.

MOEMS spatial light modulator development at the Center for Adaptive Optics

The National Science Foundation Center for Adaptive Optics (CfAO) is coordinating a program for the development of spatial light modulators suitable for adaptive optics applications based on micro-optoelectromechanical systems (MOEMS) technology. This collaborative program is being conducted by researchers at several partner institutions including the Berkeley Sensor & Actuator Center, Boston Micromachines, Boston University, Lucent Technologies, the Jet Propulsion Laboratory, and Lawrence Livermore National Laboratory. The goal of this program is to produce MEMS spatial light modulators with several thousand actuators that can be used for high-resolution wavefront control applications that would benefit from low device cost, small system size, and low power requirements. The two primary applications targeted by the CfAO are astronomy and vision science. In this paper, we present an overview of the CfAO MEMS development plan along with details of the current program status.

Simulation of an erbium-doped chalcogenide micro-disk mid-infrared laser source

The feasibility of mid-infrared (MIR) lasing in erbium-doped gallium lanthanum sulfide (GLS) micro-disks was examined. Lasing condition at 4.5 µm signal using 800 nm pump source was simulated using rate equations, mode propagation and transfer matrix formulation. Cavity quality (Q) factors of 1.48 × 10(4) and 1.53 × 10(6) were assumed at the pump and signal wavelengths, respectively, based on state-of-the-art chalcogenide micro-disk resonator parameters. With an 80 µm disk diameter and an active erbium concentration of 2.8 × 10(20) cm(-3), lasing was shown to be possible with a maximum slope efficiency of 1.26 × 10(-4) and associated pump threshold of 0.5 mW.

Semiconductor quantum-dot based wideband emitter for optical sensors

We report a novel broadband superluminescent diode using InGaAs/GaAs self-assembled quantum-dots heterostructure. The three sections superluminescent diode consists of index-guided ridge-waveguide section (4 mum wide) butt-connected to a broad-area photon absorber (50 mum wide) to minimize optical feedback and to suppress lasing action. The fabricated device produces low ripple spectrum under continuous wave operation (20 degC) with wavelength peak at ~1210 nm. The spectral bandwidth can be tuned from 71 to 94 nm by electrically addressing the individual section of device

Polysilicon surface-micromachined spatial light modulator with novel electronic integration

This paper presents a high-speed resolution phase-only microelectromechanical system (MEMS) spatial light modulator (SLM), integrated with driver electronics, using through- wafer vias and solder bump bonding. It employs a polysilicon thin film MEMS technology that is well suited to micromirror array fabrication and offers significant improvement in SLM speed in comparison to alternative modulator technologies. Vertical through-wafer interconnections offer scalability required to achieve 1M-pixel array size. The design, development, fabrication and characterization of a scalable driver integrated SLM is discussed. Pixel opto- electromechanical performance has been quantified experimentally on prototypes, and results are reported.

A Temporal Coherence Study of Quantum-Dot/Dash Broadband Lasers and Superluminescent Diodes

The temporal coherence functions of InGaAs-GaAs quantum-dot (QD) and InAs-InGaAlAs quantum-dash (Qdash) superluminescent diodes (SLDs) and broadband laser diodes (BLDs) are reported. Using an optical fiber-based spectral interferometer, the fabricated devices were shown to yield low coherence lengths of 4.00-12.29 mum and 33.48-74.56 mum for SLD and BLD devices, respectively. In addition, there were negligible secondary coherencies indicating that these devices have the potential for use in low coherent interferometric systems.