Jason K. O'Daniel

Task-based optimization and performance assessment in optical coherence imaging

Optimization of an optical coherence imaging (OCI) system on the basis of task performance is a challenging undertaking. We present a mathematical framework based on task performance that uses statistical decision theory for the optimization and assessment of such a system. Specifically, we apply the framework to a relatively simple OCI system combined with a specimen model for a detection task and a resolution task. We consider three theoretical Gaussian sources of coherence lengths of 2, 20, and 40 microm. For each of these coherence lengths we establish a benchmark performance that specifies the smallest change in index of refraction that can be detected by the system. We also quantify the dependence of the resolution performance on the specimen model being imaged.

Integrated wavelength stabilization of in-plane semiconductor lasers by use of a dual- grating reflector

We summarize a novel integrated wavelength-stabilization scheme for broad stripe surface-emitting lasers. The method is based on two gratings fabricated on opposite sides of a device in which the first grating disperses light through the substrate to the opposite side, where the second surface has a feedback grating that operates under total internal reflection and in the Littrow condition to provide feedback into the gain medium. Experimental results have been obtained for both high power and a narrow linewidth, showing a CW slope of 0.85 W/A.

High efficiency dual-wavelength surface-emitting laser incorporating integrated dual-grating reflector

We present a high-power monolithically integrated dual-wavelength emission source employing a dual-grating reflector. The basic structure and fabrication of this device are described. The operational characteristics of this device are presented, including a light-current characteristic slope of 0.86 W/A for dual-wavelength emission separated by 2 nm

Compact Vertically Stacked Master Oscillator Power Amplifier Based on Grating Coupled Laser Diodes

A new design of hybrid master oscillator power amplifier (MOPA) has been proposed and realized by vertically stacking laser diodes with optical coupling provided by identical in-plane integrated gratings. Low beam divergence, large emitting and input areas of the grating coupled devices simplify the assembling technique over the fabrication of MOPA devices based on edge-emitting laser diodes. The master oscillator also incorporates a dual-grating reflector providing a wavelength-selective feedback resulting in a narrow emission spectrum of 0.2 nm at a wavelength of 975.4 nm. The power amplifier is a tapered chip with two integrated grating couplers. The operational characteristics of the MOPA were evaluated in the pulse regime demonstrating an output peak power of 32 W with a total amplification factor of 9.3dB

Master oscillator power amplifier 3D assemblies based on grating coupled laser diodes

We report on novel architectures of the hybrid master oscillator power amplifier (MOPA) assemblies incorporating vertically stacked surface-emitting laser diodes. Optical coupling between the MO and the PA is provided by nonresonant grating couplers integrated on both of the devices. The MOPA consists of a MO chip with dual grating reflector for single wavelength operation and a flared PA chip with two grating outcouplers. Optical peak power over 100W and spectral bandwidth of 0.2nm were achieved from the single MOPA while the MO operated in the gain-switching regime and the PA operated as a traveling wave amplifier. New designs of coherent MOPA arrays are proposed based on a phase locked MO bar and a single transverse mode PA bar. This MOPA assembly requires an optical cross-coupling between the bars provided by tilted gratings which have been developed and experimentally evaluated.

Compact hybrid master oscillator power amplifier based on grating coupled laser diodes

A hybrid master oscillator power amplifier (MOPA) was fabricated from vertically stacked laser diodes with integrated grating couplers. The MO incorporated a dual grating reflector providing a narrow emission spectrum of 0.2 nm. Using a tapered amplifier, an output peak power of 32 W in the pulse regime was achieved.

Micro- and Nano-Optics in Surface Emitting Lasers

This paper investigates surface emitting lasers using nano- and micro-optics integration for spatial and spectral beam control. Specific results will be presented for beam shaping, anti-reflection coatings and intergrated-wavelength locking schemes for high power devices.

AUC-based resolution in optical coherence tomography

Optical coherence tomography (OCT) is an interferometric technique using the low coherence property of light to axially image at high resolution in biological tissue samples. Transverse imaging is obtained with two-dimensional scanning and transverse resolution is limited by the size of the scanning beam at the imaging point. The most common metrics used for determining the axial resolution of an OCT system are the full-width-at-half-maximum (FWHM), the absolute square integral (ASI), and the root-mean-square (RMS) width of the axial PSF of the system, where the PSF of an OCT system is defined as the envelope of the interference fringes when the sample has been replaced by a simple mirror. Such metrics do not take into account the types of biological tissue samples being imaged. In this paper we define resolution in terms of the instrument and the biological sample combined by defining a resolution task and computing the associated detectability index and area under the receiver operating characteristic curve (AUC). The detectability index was computed using the Hotelling observer or best linear observer. Results of simulations demonstrate that resolution is best quantified as a probability of resolving two layers, and the impact on resolution of variations in the index of refraction between the layers is clearly demonstrated.

Multi-bounce Dual Grating Reflector for Internal Wavelength Locking of Laser Diodes

This paper introduces a multi-bounce scheme based on a Dual Grating Reflector concept for integrated wavelength locking of broad stripe laser diodes.

Compact High Peak Power MOPA Assembly based on Grating Coupled Laser Diodes

A hybrid MOPA was assembled by stacking laser diodes incorporating grating couplers. Applying subnanosecond driving pulses for both MO and flared PA, optical pulses with 130 W peak power and 98 psec pulsewidth were achieved