Mckenziepugh5237

High-power tunable lasers with good longitudinal and transverse modes are fundamental tools for exploring quantum physics. Here we report a high-power continuous-wave injection-locked titaniumsapphire laser with a low-loss cavity configuration, where only a laser crystal was installed in the laser cavity. Although the transverse mode was affected by a thermal lens formed in the laser crystal, the focal length of the thermal lens could be shifted via the temperature of the laser crystal holder or the pump power. As a result, we found a condition that 10 W single-frequency oscillation with a good transverse mode and a slope efficiency of 51% were achieved.A solution to develop high-brightness incoherent sources consists in luminescent concentration. Indeed, the absorption/emission process in a high index medium allows us to circumvent the brightness conservation law by the confinement of the light in 1 or 2 dimensions. In practice, Ce-doped luminescent concentrators pumped with InGaN LED exceed LED's brightness by one order of magnitude. This work shows how light confinement in 3 dimensions increases the brightness by an additional order of magnitude. Thanks to an analytical approach validated by experimental results, this concept gives new degrees of freedom for the design of luminescent concentrators and paves the way to a generation of incoherent sources among the brightest ever designed.We theoretically investigate the second harmonic generation in tilted Dirac/Weyl semimetals with broken tilt inversion symmetry in the absence of an external magnetic field using quantum theory. An analytical formula for the second harmonic conductivity tensor is derived, and it does not depend on the chirality of Weyl node. There are two contributions to the conductivity in the low-frequency region, one coming from the intraband transitions and describing by Drude-like effects, and the other from the interband-intraband transitions due to the linear energy dispersion of Dirac/Weyl semimetals near the Dirac/Weyl points. In the high-frequency region, the appearance of prominent resonant peaks in the nonlinear conductance originates from the two-photon absorption process. It is found that Dirac/Weyl semimetals have a very high nonlinear susceptibility, and an optimal tilt of the Dirac/Weyl node for the maximum nonlinear susceptibility has been found.This paper demonstrates optical sampling by electronic repetition-rate tuning (OSBERT) a single-laser optical sampling technique capable of fast scan rates and customisable scan ranges. The method has no moving parts and is based on the electronic modulation of the repetition rate of a passively mode-locked laser diode, simply by varying the reverse bias applied directly to the saturable absorber section of the laser. Varying the repetition rate in a system built as a highly imbalanced interferometer results in pairs of (pump, probe) pulses with successive increasing delay. The resulting scan range is proportional to the magnitude of the repetition rate modulation and is scaled by the chosen length of the imbalance. As a first proof of concept, we apply the method to distance measurement, where the displacement of a target across 13.0 mm was detected with ∼0.1 mm standard deviation from an equivalent free-space distance of 36 m and at a real-time scan rate of 1 kHz. The customizable scan range and competitive scan rate of the method paves the way for single ultrafast semiconductor laser diodes to be deployed as fast, low-cost, and compact optical sampling systems in metrology, biomedical microscopy, and sensing applications.The penetration depth in a distributed Bragg reflector (DBR) co-determines the resonance condition, quality factor, and mode volume of DBR-based microcavities. Recent studies have used an incomplete description of the penetration depth and incorrect equations. We present a complete analysis that involves three different penetration depths. We also present a series of experiments on microcavities to accurately determine the frequency and modal penetration depth of our DBRs and compare these results with theoretical predictions. The obtained results are relevant for anyone who models a DBR as an effective hard mirror if lengths of the order of the wavelength are relevant, as is the case for microcavities.We present different computational approaches for the rapid extraction of the signal parameters of discretely sampled damped sinusoidal signals. We compare time- and frequency-domain-based computational approaches in terms of their accuracy and precision and computational time required in estimating the frequencies of such signals, and observe a general trade-off between precision and speed. Our motivation is precise and rapid analysis of damped sinusoidal signals as these become relevant in view of the recent experimental developments in cavity-enhanced polarimetry and ellipsometry, where the relevant time scales and frequencies are typically within the ∼1 - 10 µs and ∼1 - 100 MHz ranges, respectively. In such experimental efforts, single-shot analysis with high accuracy and precision becomes important when developing experiments that study dynamical effects and/or when developing portable instrumentations. Our results suggest that online, running-fashion, microsecond-resolved analysis of polarimetric/ellipsometric measurements with fractional uncertainties at the 10-6 levels, is possible, and using a proof-of-principle experimental demonstration we show that using a frequency-based analysis approach we can monitor and analyze signals at kHz rates and accurately detect signal changes at microsecond time-scales.We propose and investigate an all-fiber thermo-optic modulator based on a side-polished twin-core fiber (TCF) Michelson interferometer (MI) coated with NaNdF4 nanoparticles. The MI was fabricated by tapering the splicing point between the TCF and a single mode fiber (SMF). A short suspended core fiber (SCF) is spliced to one core of the TCF to introduce a fixed optical phase difference (OPD). The side-polished core is coated with photo-thermal material NaNdF4. Owing to the ohmic heating of NaNdF4 nanoparticles under 808 nm pump laser, the effective refractive index of the polished core is changed, resulting in a phase shift of the MI. The MI has a significant modulation phase shift with 2.9 π near the wavelength of 1260 nm and can obtain an optical switching with a rise (fall) time of 152 (50) ms. The proposed device will have a great application potential in optical modulators due to compact structure and strong robustness.A method for modeling the irradiance spatial distribution by light-emitting diodes (LEDs) on near distance targets has been developed. The model can easily handle the complex simulation of non-homogenous emitting LEDs, multichip LEDs, LED arrays, and phosphor coated LEDs. The LED irradiation profile is obtained by image processing one photograph of the emitting LED, taken with a smartphone. The method uses image convolution or image correlation between the LED image and a special kernel. The model provides the irradiation spatial pattern in function of the irradiation distance. And the model is tested both with theory and with experimental measurements.In recent development of quantum technologies, a frequency conversion of quantum signals has been studied widely. We investigate the optic-microwave entanglement that is generated by applying an electro-optomechanical frequency conversion scheme to one mode in an optical two-mode squeezed vacuum state. We quantify entanglement of the converted two-mode Gaussian state, where surviving entanglement of the state is analyzed with respect to the parameters of the electro-optomechanical system. Furthermore, we show that there exists an upper bound for the entanglement that survives after the conversion of highly entangled optical states. Our study provides a theoretical platform for a practical quantum illumination system.We have fabricated a Si racetrack optical modulator based on a III-V/Si hybrid metal-oxide-semiconductor (MOS) capacitor. The III-V/Si hybrid MOS optical phase shifter was integrated to a Si racetrack resonator with a coupling length of 200 µm and a coupling gap of 700 nm. The fabricated Si racetrack resonator demonstrated a small VπL of 0.059 Vcm. For 10-dB optical intensity modulation, the Si racetrack resonator showed a 60% smaller driving voltage than a Mach-Zehnder interferometer modulator with the same phase shifter, leading to a better balance between high energy efficiency and large modulation bandwidth.In this paper, a novel approach to modelling intracavity second harmonic generation (SHG) in periodically poled MgO-doped lithium niobate (PPLN) is presented and verified against experimental results. This approach involves combining the coupled nonlinear wave equations with a rate equation model for a diode-pumped solid-state NdYVO4 laser, taking into account both the depletion of the fundamental wave due to the energy conversion from the fundamental wave to the SHG wave and the reduction of the fundamental wave within a laser cavity due to the loss as a result of the SHG nonlinear process. It was shown that the theoretical simulation matched the experimental results well, while also providing physical insight into the importance of the fundamental wave depletion in the intracavity SHG nonlinear processes. Apoptosis activator The resulting model is computationally simple and has the potential to generalize to the other nonlinear processes such as three-wave mixing and optical parametric oscillation.In this paper, a characteristic mode rotation (CMR) method has been proposed to design a compact metasurface antenna with a low radar cross section (RCS) in a wideband. In the proposed CMR method, the incident wave dependent complex characteristic currents corresponding to the dominant characteristic modes solved by the characteristic mode method (CMM) are calculated. With the direction of the superposition of the complex characteristic currents orthogonal to that of the incident electric field in the CMR method, the metasurface subarray with wideband polarization conversion characteristic is designed. By arranging the metasurface subarray in a rotation way, a metasurface array with a compact size of 1.28λ0×1.28λ0 is designed for wideband RCS reduction. A miniature circle patch antenna is integrated with the metasurface array to achieve not only good radiation performance but also low observability for the in-band and the out-of-band of the antenna. Simulated and measured results demonstrate that the proposed miniature metasurface antenna designed by the CMR method has a good broadside radiation pattern, a maximal gain of 10.75 dB, and a -10 dB RCS reduction characteristic in the wide band of 6∼20.7 GHz with a fractional band of 110%.In order to increase the number of detectable gravitational-wave sources, future gravitational-wave detectors will operate with cryogenically cooled mirrors. link2 However, recent studies showed that cryogenic mirrors can suffer from the molecular layer formation, which introduces an additional optical loss, and the detector's performance degrades. link3 In order to evaluate the impact of the molecular layer on future cryogenic gravitational-wave detectors, we built a cryogenic folded-cavity setup and developed an ellipsometric measurement method. The optical loss induced by the cryogenic molecular layer shows a large value even at a few nanometer thickness and can deteriorate the performance of the future cryogenic gravitational-wave detectors.