Circularly Polarized Stimulated Emission from a Chiral Cavity Based on Apparent Circular Dichroism Organic Thin-Films
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Closed cycle electric discharge laser design investigation
Closed cycle CO2 and CO electric discharge lasers were studied. An analytical investigation assessed scale-up parameters and design features for CO2, closed cycle, continuous wave, unstable resonator, electric discharge lasing systems operating in space and airborne environments. A space based CO system was also examined. The program objectives were the conceptual designs of six CO2 systems and one CO system. Three airborne CO2 designs, with one, five, and ten megawatt outputs, were produced. These designs were based upon five minute run times. Three space based CO2 designs, with the same output levels, were also produced, but based upon one year run times. In addition, a conceptual design for a one megawatt space based CO laser system was also produced. These designs include the flow loop, compressor, and heat exchanger, as well as the laser cavity itself. The designs resulted in a laser loop weight for the space based five megawatt system that is within the space shuttle capacity. For the one megawatt systems, the estimated weight of the entire system including laser loop, solar power generator, and heat radiator is less than the shuttle capacity.
Baily, P. K.↗
Long-Gain-Length, Solar-Pumped Box Laser
New laser cavity configuration efficiently couples solar radiation to laser mode volume. Lasing output powers of approximately 300 mW achieved for durations of 150 ms. New system allows lasing at substantially lower solar simulator intensities (150 Suns) and much longer laser gain lengths (60 cm).
De Young, R. J.↗
Analysis of the Spontaneous Emission Limited Linewidth of an Integrated III–V/SiN Laser
Abstract This article describes a calculation of the spontaneous emission limited linewidth of a semiconductor laser consisting of hybrid or heterogeneously integrated, silicon and III–V intracavity components. Central to the approach are a) description of the multi‐element laser cavity in terms of composite laser/free‐space eigenmodes, b) use of multimode laser theory to treat mode competition and multiwave mixing, and c) incorporation of quantum‐optical contributions to account for spontaneous emission effects. Application of the model is illustrated for the case of linewidth narrowing in an InAs quantum‐dot laser coupled to a high‐ SiN cavity.
42 ENGINEERING↗
Stabilized Nd:YAG laser output
Stabilization system consists of feedback-loop-controlled piezoelectric crystal to one of the reflectors to vary optical path length within laser cavity. Average second harmonic of fundamental 1.06 micrometer laser radiation is detected by integrating detector.
Osmundson, J.↗
Kilowatt multiple-path He-3-Ar nuclear-pumped laser
Nuclear lasing of He-3-Ar at 2300-torr total pressure with a thermal neutron flux of 4.3 x 10 to the 16th n/sq cm-sec has resulted in a lasing output power of 1012 W. A multiple-path laser cavity was used with seven passes through the laser medium which was pumped by the He-3(n, p)H-3 nuclear reaction. The thermal neutron lasing threshold flux was 1 x 10 to the 16th n/sq cm-sec. At 600-Torr He-3-(2%)Ar, the threshold flux was 4.7 x 10 to the 15th n/sq cm-sec. This represents the highest-power, largest-volume nuclear laser to date.
Deyoung, R. J.↗
Tunable Metasurface External-Cavity Quantum Cascade Lasers up to 5.74 THz
Vertical-external-cavity surface-emitting lasers based on amplifying quantum-cascade metasurfaces are demonstrated in the 5–6 THz range for the first time. Enhanced parasitic coupling to lossy surface modes requires updated design guidelines, while elevated losses and lower available material gain limit the scaling of the metasurface period from previous designs. A series of metasurface devices with varying periods employing both uniform and focusing metasurfaces is fabricated and characterized. Reducing the metasurface period below 70% of the free-space wavelength enables devices with superior performance, achieving pulsed operation up to 5.74 THz with peak output powers of 1.3 mW, maximum operating temperatures up to 83 K, and continuous-wave operation up to 54 K with 23 μW of output power. In the best case, single-mode tuning from 5.23–5.73 THz, which corresponds to a 9.1% fractional tuning, is realized with near-Gaussian far-field profiles maintained across the entire range. Finally, these results establish quantum cascade vertical-external-cavity surface-emitting lasers as promising candidates for high-frequency local oscillator applications in heterodyne spectroscopy.
gallium arsenide↗
Parametric thermodynamic analysis of closed-cycle gas-laser operation in space
Cycle efficiency and radiator area required were calculated for thermally and electrically pumped lasers operating in closed cycles with a compressor and the required heat exchangers. A thermally pumped laser included within a Brayton cycle was also analyzed. Performance of all components, including the laser, was parametrically varied. For the thermally pumped laser the cycle efficiencies range below 10 percent and are very sensitive to the high-pressure losses associated with the supersonic diffuser required at the laser cavity exit. The efficiencies predicted for the electrically pumped laser cycles range slightly higher, but radiator area also tends to be larger.
Burns, R. K.↗
Optical feedback effects on the performance of Pb/1-x/Sn/x/Se semiconductor lasers
The effects of optical feedback on the performance of Pb(1-x)Sn(x)Se semiconductor lasers are reported. Experimental results are presented to demonstrate that uncontrolled optical feedback can occur from optics external to the laser cavity and that these external optical elements can result in the formation of a composite cavity. This composite cavity can sustain a number of narrow closely spaced emission modes with the spectral characteristics of these modes dependent upon the parameters of the cavity. With weak feedback, the spectral width of the amplitude envelope of the new lasing modes resembles that of the original laser mode with no optical feedback. With strongly coupled feedback the envelope of the external cavity modes substantially broadens the apparent linewidth of the laser. It is shown that these effects can be eliminated, and, moreover, they offer the potential for obtaining spectrally narrow single-mode emission from Pb-salt lasers through the use of carefully designed external cavities.
Harward, C. N.↗
Dual-polarized ring lasers
Simultaneous laser oscillation of four nondegenerate polarization and propagation direction eigenstates of a single TEM-00 mode was observed in a ring laser cavity. The observed polarization and frequency properties of the ring laser were analyzed in terms of the Jones matrix calculus.
Sanders, V. E.↗
Line spread instrumentation for propagation measurements
A line spread device capable of yielding direct measure of a laser beam's line spread function (LSF) was developed and employed in propagation tests conducted in a wind tunnel to examine optimal acoustical suppression techniques for laser cavities exposed to simulated aircraft aerodynamic environments. Measurements were made on various aerodynamic fences and cavity air injection techniques that effect the LSF of a propagating laser. Using the quiescent tunnel as a control, the relative effect of each technique on laser beam quality was determined. The optical instrument employed enabled the comparison of relative beam intensity for each fence or mass injection. It was found that fence height had little effect on beam quality but fence porosity had a marked effect, i.e., 58% porosity alleviated cavity resonance and degraded the beam the least. Mass injection had little effect on the beam LSF. The use of a direct LSF measuring device proved to be a viable means of determining aerodynamic seeing qualities of flow fields.
Bailey, W. H., Jr.↗
A tunable coherent CO2 lidar for measurements of atmospheric aerosol backscatter and attenuation
A coherent laser radar system using a grating-tunable, injection-locked TEA-CO2 transmitter is being used to measure the altitude dependence of atmospheric aerosol backscatter and attenuation at a variety of CO2 laser wavelengths in the 9-11 micron region. Injection control of the TEA-CO2 laser allows one to obtain Single-Longitudinal-Mode (SLM) pulses which will follow the frequency of the injected radiation if the TEA laser cavity length is adjusted so that a cavity resonance is in proximity with the injected signal frequency, and if various additional conditions are satisfied. Requirements for generation of SLM pulses in this manner from a TEA CO2 laser with an unstable resonator cavity will be discussed. Procedures used for quantitative range-gated measurements of aerosol backscatter and attenuation will also be discussed.
Menzies, R. T.↗
Folded cavity design for a ruby resonator
A folded cavity laser resonator operating in the TEM(00) mode has been built and tested. The new oscillator configuration leads to an increase in efficiency and to better line narrowing due to the increased number of passes through the laser rod and tuning elements, respectively. The modification is shown to lead to cavity ruggedization.
Arunkumar, K. A.↗
Laser Sources for Generation of Ultrasound
Two laser systems have been built and used to demonstrate enhancements beyond current technology used for laser-based generation and detection of ultrasound. The first system consisted of ten Nd:YAG laser cavities coupled electronically and optically to permit sequential bursts of up to ten laser pulses directed either at a single point or configured into a phased array of sources. Significant enhancements in overall signal-to-noise ratio for laser ultrasound incorporating this new source system was demonstrated, using it first as a source of narrowband ultrasound and secondly as a phased array source producing large enhanced signal displacements. A second laser system was implemented using ultra fast optical pulses from a Ti:Sapphire laser to study a new method for making laser generated ultrasonic measurements of thin films with thicknesses on the order of hundreds of angstroms. Work by prior investigators showed that such measurements could be made based upon fluctuations in the reflectivity of thin films when they are stressed by an arriving elastic pulse. Research performed using equipment purchased under this program showed that a pulsed interferometric system could be used as well as a piezoreflective detection system to measure pulse arrivals even in thin films with very low piezoreflective coefficients.
Wagner, James W.↗
Amplitude Noise Reduction of Ion Lasers with Optical Feedback
A reduction in amplitude noise on the output of a multi-mode continuous-wave Ar-ion laser was previously demonstrated when a fraction of the output power was retroreflected back into the laser cavity. This result was reproduced in the present work and a Fabry-Perot etalon was used to monitor the longitudinal mode structure of the laser. A decrease in the number of operating longitudinal cavity modes was observed simultaneously with the introduction of the optical feedback and the onset of the amplitude noise reduction. The noise reduction is a result of a reduced number of lasing modes, resulting in less mode beating and amplitude fluctuations of the laser output power.
Herring, Gregory C.↗
Spectral narrowing and broadening of Cr:ZnS/Se laser oscillation due to mode competition and spatial hole burning in the gain element
In this paper, we demonstrate the laser characterization of Cr:ZnS/Se polycrystalline gain media in non-selective unpolarized, linearly polarized, and twisted mode cavities. Lasers were based on post-growth diffusion-doped, commercially available antireflective-coated Cr:ZnSe and Cr:ZnS polycrystals with a length of 9 mm. The spectral output of lasers based on these gain elements in non-selective unpolarized and linearly polarized cavities was measured to be broadened to ∼20-50 nm due to the spatial hole burning (SHB) effect. SHB alleviation in the same crystals was realized in the “twisted mode” cavity, with linewidth narrowing to ∼80-90 pm. Both broadened and narrow-line oscillations were captured by adjusting the orientation of intracavity waveplates with respect to facilitated polarization.
47 OTHER INSTRUMENTATION↗
Optimizing coherent lidar performance with graded-reflectance laser resonator optics
It is demonstrated how the design of graded-reflectance output coupler unstable laser cavities may be tailored to significantly enhance the overall power transmission efficiency of a given laser system relative to that of a conventional diffractively coupled unstable resonator. The importance of these findings in coherent lidar applications is explained with particular emphasis on projected space-based systems.
Tratt, David M.↗
Fourier-method beam analysis for coherent vertical cavity surface emitting laser arrays
Effective engineering and exploitation of coherently coupled vertical cavity surface emitting laser arrays will benefit from simple and fast characterization of the optical coupling and coherence. We propose a Fourier method of analyzing beam profiles as an alternative to the prior beam visibility analysis and show that the mode suppression ratio and phase between a pair of supermodes can be extracted. Our analysis enables fast quantitative determination of the array coherence and supermode characteristics.
Strzebonski, Pawel (ORCID:0000000156286296)↗