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Leshin J.,sdPhotonics LLC | Li M.,University of Central Florida | Beadsworth J.,sdPhotonics LLC | Yang X.,University of Central Florida | And 5 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

Sensing applications along with free space data links can benefit from advanced laser sources that produce novel radiation patterns and tight spectral control for optical filtering. Vertical-cavity surface-emitting lasers (VCSELs) are being developed for these applications. While oxide VCSELs are being produced by most companies, a new type of oxide-free VCSEL is demonstrating many advantages in beam pattern, spectral control, and reliability. These lithographic VCSELs offer increased power density from a given aperture size, and enable dense integration of high efficiency and single mode elements that improve beam pattern. In this paper we present results for lithographic VCSELs and describes integration into military systems for very low cost pulsed applications, as well as continuouswave applications in novel sensing applications. The VCSELs are being developed for U.S. Army for soldier weapon engagement simulation training to improve beam pattern and spectral control. Wavelengths in the 904 nm to 990 nm ranges are being developed with the spectral control designed to eliminate unwanted water absorption bands from the data links. Multiple beams and radiation patterns based on highly compact packages are being investigated for improved target sensing and transmission fidelity in free space data links. These novel features based on the new VCSEL sources are also expected to find applications in 3-D imaging, proximity sensing and motion control, as well as single mode sensors such as atomic clocks and high speed data transmission. © 2016 SPIE.


Yang X.,University of Central Florida | Zhao G.,sdPhotonics LLC | Li M.,University of Central Florida | Deppe D.,University of Central Florida | Deppe D.,sdPhotonics LLC
Electronics Letters | Year: 2015

Reliability test data are presented, which show that non-oxide all-lithographic vertical-cavity surface-emitting lasers (VCSELs) are more reliable than oxide VCSELs under extreme operating conditions. The test data are compared for lithographic and oxide VCSELs of 3 μm size after operating at a stage temperature of 150°C and an injection current density of 140 kA/cm2 for various times. The increased reliability under extreme operating conditions can be largely attributed to the lower junction temperature and the internal stress inside lithographic VCSELs. © The Institution of Engineering and Technology 2015.


Demir A.,University of Central Florida | Demir A.,sdPhotonics LLC | Zhao G.,University of Central Florida | Freisem S.,University of Central Florida | And 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

Data are presented demonstrating lithographic vertical-cavity surface-emitting lasers (VCSELs) and their scaling properties. Lithographic VCSELs have simultaneous mode- and current-confinement defined only by lithography and epitaxial crystal growth. The lithographic process of these devices allows getting uniform device size throughout a wafer and easy scaling to manufacture very small lasers. The semiconductor's high thermal conductivity enables the small lithographic VCSEL to have lower thermal resistance than an oxide-aperture VCSEL, while the lithographic fabrication produces high VCSEL uniformity even at small size. Very dense packing is also possible. Devices of 3 μm to 20 μm diameters are fabricated and scaling properties are characterized. 3 μm lithographic VCSELs produce output power of 4.1 mW, with threshold current of 260 μA and slope efficiency of 0.76 W/A at emission wavelength of ~980 nm. These VCSELs also have single-mode single-polarization lasing without the use of a surface grating, and have >25 dB sidemode- suppression-ratio up to 1 mW of output power. Lifetime tests demonstrate that 3 μm VCSEL operates for hundreds of hours at high injection current level of 85 kA/cm2 with 3.7 mW output power without degradation. Scaling properties and low thermal resistance of the lithographic VCSELs can extend the VCSEL technology to manufacturable and reliable small size lasers and densely packed arrays with long device lifetime. © 2011 Copyright SPIE - The International Society for Optical Engineering.


Yang X.,University of Central Florida | Li M.,University of Central Florida | Zhao G.,sdPhotonics LLC | Zhang Y.,University of Central Florida | And 4 more authors.
Electronics Letters | Year: 2014

Data are presented showing that lithographic vertical-cavity surfaceemitting lasers (VCSELs) produce minimal junction temperature rise compared to oxide VCSELs. Eliminating the thermal block caused by internal oxides combined with improved mirror materials reduces the junction temperature. The elimination of internal oxide, lower junction temperature and reduced internal strain promise increased reliability in the new VCSELs. Power conversion efficiencies in excess of ∼50% are reported, even for very small lithographic VCSELs. © 2014 The Institution of Engineering and Technology.


Deppe D.,University of Central Florida | Deppe D.,sdPhotonics LLC | Zhao G.,sdPhotonics LLC | Li M.,University of Central Florida | Yang X.,University of Central Florida
2015 IEEE Summer Topicals Meeting Series, SUM 2015 | Year: 2015

Removal of oxide layers from the VCSEL and incorporating AlAs in the low index mirror layers can dramatically decrease the VCSEL's thermal resistance, and has been shown to increase the stimulated emission rate [1]. These can be scaled down to a much smaller size and maintain high efficiency [2]. Therefore with smaller size, the electrical parasitics can also be reduced. © 2015 IEEE.


Grant
Agency: Department of Defense | Branch: Army | Program: SBIR | Phase: Phase II | Award Amount: 500.00K | Year: 2015

The Armys Multiple Integrated Laser Engagement Simulation (iMILES) currently uses a 904.5 nm wavelength laser link along with silicon photodiodes at a receiver (target). Several improvements are expected in the laser link capability with a change from 904.5 nm to the 1550 nm wavelength. One dramatic improvement could be range finding during line of sight tactical engagement. Range finding can improve situational awareness in the Armys simulation and training exercises, and eliminate the need for detector threshold to achieve roll-off. Additional improvements include improved atmospheric propagation of the laser pulses, reduced noise from background lighting, increased transmission through battlefield obscurants, increased eye-safety, and increased data rate.


Grant
Agency: Department of Defense | Branch: Defense Advanced Research Projects Agency | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2012

A new facet coating material for high power diode lasers will be developed that reduces interface states at the cleaved facet and increases facet cooling. The facet coating is expected to be more robust and lead to increased power and brightness in high power diode lasers, bars and stacks. The facet coating technique makes use of commercial processes based on vacuum cleaving and epitaxial growth, and can be used to add optical elements to improve beam quality and spectral control.


Grant
Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase I | Award Amount: 80.00K | Year: 2012

High quality laser materials based on InP, InGaAs, InAlGaAs, and InAs are proposed to develope high power 3 to 3.5 m diode lasers. An adiabatically broadened amplifying section is proposed to reach high power with high beam quality. The active material uses strained layer epitaxy to rely only on high quality laser materials that can be grown by molecular beam epitaxy, and with high quality on InP substrates. Highly strained active layer can lead to rapid commercial production because of compatibility with existing military suppliers of diode laser epitaxy.


Grant
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 150.00K | Year: 2012

ABSTRACT: A new active material will be developed and tested to improve reliability for space applications. Recent improvement in facet reliability reveals that bulk failure mechanisms could limit laser diodes used in space. Radiation-induced defects are expected to occur in the bulk of the laser diode gain material because of its active volume. The new active material is designed to limit internal heating at defects, and reduce the average junction temperature relative to the heat sink temperature. Preliminary studies on cleaved facet laser diodes indicate that with further improvement in active material quality, high quality facet coating, and high quality heat sinking, power and efficiency could reach or exceed commercial laser diodes. A Phase I is proposed to optimize the gain material and waveguide design to produce prototype devices for detailed reliability and radiation studies in a Phase II. Full optimization of the active material physics could produce laser diodes with electro-optic properties superior to commercial laser diode pumps. The combined improvements in bulk reliability and electro-optic performance could lead to rapid commercialization into the military and industrial laser diode markets. BENEFIT: The current commercial high power laser diode technology is highly developed and only incremental improvements are expected by maintaining the current active material and device designs. Many military applications can benefit from higher powers that could be possible by introducing new designs. These new designs should produce higher reliability, less susceptibility to radiation induced-defects for space applications, and lower internal optical loss to give the potential for higher power and efficiency. The new materials to be researched and developed in this research effort can bring these advantages by changing the internal laser device physics from the current planar quantum wells.


Grant
Agency: Department of Defense | Branch: Army | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2013

A new approach to the Army Tactical Engagement Simulation System (TESS) is proposed to increase the link reliability, increase range, and increase the amount of data that can be transferred. The new technology uses both laser sources and detectors with improved propagation properties that meet eye-safety requirements, and meet the cost requirements for TESS laser systems. The new technology offers the prospect of increasing both the laser power and link efficiency by overcoming scintillation and fading problems due to atmospheric turbulence characteristic of battlefield training. Efficiency and the amount of data transferred under engagement pairing may both be increased by utilizing new coding schemes with the lasers and detectors, along with improved digital signal processing. Increased range while retaining important information related to roll-off also appears possible. New techniques to extend battery lifetime will be explored, along with detailed simulation of the expected results and component testing. If successful, field-testing of the new technology is anticipated in a Phase II effort.

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