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Spectral imaging with dual compressed sensing  [PDF]
Xue-Feng Liu,Wen-Kai Yu,Xu-Ri Yao,Bin Dai,Long-Zhen Li,Chao Wang,Guang-Jie Zhai
Physics , 2015,
Abstract: We experimentally demonstrated a spectral imaging scheme with dual compressed sensing. With the dimensions of spectral and spatial information both compressed, the spectral image of a colored object can be obtained with only a single point detector. The effect of spatial and spectral modulation numbers on the imaging quality is also analyzed. Our scheme provides a stable, highly consistent approach of spectral imaging.
Low-spatial coherence electrically-pumped semiconductor laser for speckle-free full-field imaging  [PDF]
B. Redding,A. Cerjan,X. Huang,M. L. Lee,A. D. Stone,M. A. Choma,H. Cao
Physics , 2014, DOI: 10.1073/pnas.1419672112
Abstract: The spatial coherence of laser sources has limited their application to parallel imaging and projection due to coherent artifacts, such as speckle. In contrast, traditional incoherent light sources, such as thermal sources or light emitting diodes (LEDs), provide relatively low power per independent spatial mode. Here, we present a chip-scale, electrically-pumped semiconductor laser based on a novel design, demonstrating high power per mode with much lower spatial coherence than conventional laser sources. The laser resonator was fabricated with a chaotic, D-shaped cavity optimized to achieve highly multimode lasing. Lasing occurs simultaneously and independently in ~1000 modes, and hence the total emission exhibits very low spatial coherence. Speckle-free full-field imaging is demonstrated using the chaotic cavity laser as the illumination source. The power per mode of the sample illumination is several orders of magnitude higher than that of a LED or thermal light source. Such a compact, low-cost source, which combines the low spatial coherence of a LED with the high spectral radiance of a laser, could enable a wide range of high-speed, full-field imaging and projection applications.
Semiconductor Optical Amplifier (SOA)-Fiber Ring Laser and Its Application to Stress Sensing  [PDF]
Yoshitaka Takahashi, Shinji Sekiya, Tatsuro Suemune
Optics and Photonics Journal (OPJ) , 2011, DOI: 10.4236/opj.2011.14027
Abstract: We have developed a novel optical fiber ring laser using a semiconductor optical amplifier (SOA) as the gain medium, and taking advantage of polarization anisotropy of its gain. The frequency difference of the bi-directional laser is controlled by birefringence which is introduced in the ring laser cavity. The beat frequency generated by combining two counter-propagating oscillations is proportional to the birefringence, the fiber ring laser of the present study is, therefore, applicable to the fiber sensor. The sensing signal is obtained in a frequency domain with the material which causes the retardation change by a physical phenomenon to be measured. For the application to stress sensing, the present laser was investigated with a photoelastic material.
Photoacoustic Techniques for Trace Gas Sensing Based on Semiconductor Laser Sources  [PDF]
Angela Elia,Pietro Mario Lugarà,Cinzia Di Franco,Vincenzo Spagnolo
Sensors , 2009, DOI: 10.3390/s91209616
Abstract: The paper provides an overview on the use of photoacoustic sensors based on semiconductor laser sources for the detection of trace gases. We review the results obtained using standard, differential and quartz enhanced photoacoustic techniques.
Near-IR Spectral Imaging of Semiconductor Absorption Sites in Integrated Circuits  [cached]
E. C. Samson,C. M. Blanca,Caesar Saloma
Science Diliman , 2004,
Abstract: We derive spectral maps of absorption sites in integrated circuits (ICs) by varying the wavelength of the optical probe within the near-IR range. This method has allowed us to improve the contrast of the acquired images by revealing structures that have a different optical absorption from neighboring sites. A false color composite image from those acquired at different wavelengths is generated from which the response of each semiconductor structure can be deduced. With the aid of the spectral maps, nonuniform absorption was also observed in a semiconductor structure located near an electrical overstress defect. This method may prove important in failure analysis of ICs by uncovering areas exhibiting anomalous absorption, which could improve localization of defective edifices in the semiconductor parts of the microchip
The Waveform Digitization of Laser Return in Airborne Laser Remote Sensing Imaging

HU Yi-hu,WANG Jian-yu,XUE Yong-qi,

遥感学报 , 2001,
Abstract: The fundamentals of airborne laser remote sensing imaging technology is introduced first in this paper. As a key part of the technology, the waveform digitizing circuit for acquiring laser return of ground targets is designed and its features are discussed. Then how to control digitizing and how to store digitized data are described. Finally some problems about pre_processing of digitized data are discussed and some typical results are given. The pre_processed results will be used as data sources to directly produce 3_D image and to sort ground objects.
DFB Lasers Between 760 nm and 16 μm for Sensing Applications  [PDF]
Wolfgang Zeller,Lars Naehle,Peter Fuchs,Florian Gerschuetz,Lars Hildebrandt,Johannes Koeth
Sensors , 2010, DOI: 10.3390/s100402492
Abstract: Recent years have shown the importance of tunable semiconductor lasers in optical sensing. We describe the status quo concerning DFB laser diodes between 760 nm and 3,000 nm as well as new developments aiming for up to 80 nm tuning range in this spectral region. Furthermore we report on QCL between 3 μm and 16 μm and present new developments. An overview of the most interesting applications using such devices is given at the end of this paper.
Octave-spanning semiconductor laser  [PDF]
Markus R?sch,Giacomo Scalari,Mattias Beck,Jér?me Faist
Physics , 2014, DOI: 10.1038/nphoton.2014.279
Abstract: We present here a semiconductor injection laser operating in continuous wave with an emission covering more than one octave in frequency, and displaying homogeneous power distribution among the lasing modes. The gain medium is based on a heterogeneous quantum cascade structure operating in the THz range. Laser emission in continuous wave takes place from 1.64 THz to 3.35 THz with optical powers in the mW range and more than 80 modes above threshold. Free-running beatnote investigations on narrow waveguides with linewidths of 980 Hz limited by jitter indicate frequency comb operation on a spectral bandwidth as wide as 624 GHz, making such devices ideal candidates for octave-spanning semiconductor-laser-based THz frequency combs.
Fast dynamics and spectral properties of a multilongitudinal-mode semiconductor laser: evolution of an ensemble of driven, globally coupled nonlinear modes  [PDF]
G. P. Puccioni,G. L. Lippi
Physics , 2014,
Abstract: We analyze the fast transient dynamics of a multi-longitudinal mode semiconductor laser on the basis of a model with intensity coupling. The dynamics, coupled to the constraints of the system and the below-threshold initial conditions, imposes a faster growth of the side modes in the initial stages of the transient, thereby leading the laser through a sequence of states where the modal intensity distribution dramatically differs from the asymptotic one. A detailed analysis of the below-threshold, deterministic dynamical evolution allows us to explain the modal dynamics in the strongly coupled regime where the total intensity peak and relaxation oscillations take place, thus providing an explanation for the modal dynamics observed in the slow, hidden evolution towards the asymptotic state (cf. Phys. Rev. A 85, 043823 (2012)). The dynamics of this system can be interpreted as the transient response of a driven, globally coupled ensemble of nonlinear modes evolving towards an equilibrium state. Since the qualitative dynamics do not depend on the details of the interaction but only on the structure of the coupling, our results hold for a whole class of globally, bilinearly coupled oscillators.
Limits of Modal Insensitivity for Laser Vibrometry, spectral reduction requires super-symmetry  [PDF]
Michael C. Kobold
Physics , 2014,
Abstract: Lab measurements showed that identification (ID) and monitoring of objects using remote sensing of their vibration signatures are limited in a couple rare cases. This work provides two necessary conditions to infer that the identification of practical targets to within prescribed bounds; failure to ID the spectrum is shown to be rare. Modal modulation of laser return produces data clusters for adequate spectral ID using slowly swept sine (SSS) and small deflection multi-modal (MM) analyses. Results using these completely different calculations lead to practical removal of a remote sensing concern, spectral "reduction" (SR) of return used for object ID. The optical return provides structural mode ID for non-imaging detection and classification. Calculations using a large spot size to completely paint the vibrating object provide insight for SR found in laboratory measurements which use spot size as a variable. Non-imaging calculations comparing SSS and MM approximations show vibrating rectangular plates have spatially integrated (non-imaging) return that varies substantially among low-frequency vibration modes. The clustering of data from these two methods are the necessary conditions for ID. Theories for SSS and MM describe the signal processing physics for a modal recognition capability and how pure one-dimensional modal targets and super-symmetric square plates can frustrate classification.
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