Search

We demonstrate an experimental and theoretical comparison of non-oxide LiGaS2, HgGa2S4, and AgGaS2 crystals performance for wavelength conversion into the near and mid-IR range 1.5–8 μm in optical parametric amplifier pumped by Cr:Forsterite laser, delivering 100 fs pulses at 1.24 μm. It is shown that exceptionally high total energy conversion efficiency into the idler (4–5 μm) and signal (1.65–1.8 μm) waves up to 18% can be achieved using the HGS crystal, providing high nonlinearity, while the LGS crystal is more preferable for generating few-cycle mid-IR pulses due its unique dispersive properties. Our source features high peak power in gigawatt regime (0.4–2.4 GW) with pulse duration below 80 fs and optical synchronization with high harmonic generation (HHG) and THz beamlines, which is ideal for pump-probe experiments of nonlinear and strong-field physics. [ABSTRACT FROM AUTHOR]

We report an experimental scheme for stimulated Raman scattering (SRS) microscopy with excitation in the visible spectral region. This allows electronically preresonant (epr) SRS microscopy of a broad range of chromophores with sensitivities as low as 1 μM. Our experiment is based on two synchronously near-infrared pumped optical parametric oscillators (OPO). One of the outputs is modulated at a fourth of the repetition rate with a novel broadband electro-optical modulator. Using a combination of spectral focusing and tuning of the OPO, we show the recording of epr-SRS spectra over the whole range of molecular vibrations at a speed up to 20 times faster than classical wavelength tuning. The imaging capabilities of this setup are demonstrated with material scientific and cellular samples. [ABSTRACT FROM AUTHOR]

We report on the generation of an off-axis vortex with tunable non-integer orbital angular momentum (OAM), generated using an idler-resonant mid-infrared optical parametric oscillator (OPO) based on KTiOAsO4. The design of the OPO enables the OAM of the signal and idler outputs to be varied from 0 to 1 through precise adjustment of cavity length. The maximum vortex output energies at 1.5 and 3.5 μm were 1.95 and 1.1 mJ, respectively, and were obtained at a maximum pump energy of 20 mJ. The means by which the OAM was shared between the signal and idler fields was theoretically examined by modeling the spatial coupling among the pump, signal, and idler fields within the cavity. This work offers a unique means by which exotic vortex laser beams with tunable non-integer OAM can be generated and tuned simply through cavity length adjustments. [ABSTRACT FROM AUTHOR]

We report a resonant torsional micro-mirror with all-piezoelectric driving and tunable spring stiffness. Stiffness modulation finds two practical applications. First is tuning of the resonance frequency, achieved by applying DC bias voltage to the stiffness modulating structures. A tuning rate was found to be 0.95 Hz V−1 with up to 20 Hz of usable frequency range. Second, when direct excitation of the torsional mode is combined with the harmonic modulation of the spring stiffness, an optical scan angle is shown to be increased by more than 4° through 2:1 degenerate parametric amplification. By varying the phase of the parametric pump with respect to the direct excitation, the Q-factor is tuned between 617 and 898, corresponding to the minimum and maximum parametric gain factors of 0.84× and 1.21×, respectively, achieved at a nominal unpumped optical scan angle of 16.3°. Increasing the pump amplitude shows a moderate increase in the amplifier's gain with clear saturation at 1.43× in the superthreshold pumping regime, indicating a presence of the third order stiffness nonlinearity. The results show potential to apply parametric amplification to future piezo-micro-electro-mechanical-system actuators for large frequency and large-stroke mechanical response achieved at ambient pressure. [ABSTRACT FROM AUTHOR]

The magnetic skyrmion-based spin transfer nano-oscillators have been set as microwave signal emitters and gaining in popularity due to their performance and integrability in the existing CMOS process flow. In this work, we report our investigations on the strain-modulated magnetization precession in the breathing mode skyrmion-based spin transfer nano-oscillator, which strains from the juxtaposed piezoelectric materials. The strain-modulated skyrmion breathing frequency can be strongly controlled by biaxial-isotropy in-plane strain, in which the tunable range varies from 500 MHz to 7 GHz under the fixed current density − 4 × 10 12 A / m 2 and varying strain from − 2000 ppm to 4000 ppm. Such tunability is external magnetic free and even does not reduce the dynamic resistance variation. Through this method, a promising digital binary frequency shift-key and amplitude shift-key modulation technique are presented, in which the magnetization precession frequency and amplitude can be tuned with the co-action of current and strain pulses. These findings are providing an optional route to design future tunable spin transfer nano-oscillators based on skyrmion with better performance in the wireless communication. [ABSTRACT FROM AUTHOR]

A coherent Ising machine (CIM) is a network of optical parametric oscillators (OPOs), in which the "strongest" collective mode of oscillation at well above threshold corresponds to an optimum solution of a given Ising problem. When a pump rate or network coupling rate is increased from below to above threshold, however, the eigenvectors with the smallest eigenvalue of the Ising coupling matrix [ J i j ] appear near threshold and impede the machine to relax to true ground states. Two complementary approaches to attack this problem are described here. One approach is to utilize the squeezed/anti-squeezed vacuum noise of OPOs below threshold to produce coherent spreading over numerous local minima via quantum noise correlation, which could enable the machine to access either true ground states or excited states with eigen-energies close enough to that of ground states above threshold. The other approach is to implement a real-time error correction feedback loop so that the machine migrates from one local minimum to another during an explorative search for ground states. Finally, a set of qualitative analogies connecting the CIM and traditional computer science techniques are pointed out. In particular, belief propagation and survey propagation used in combinatorial optimization are touched upon. [ABSTRACT FROM AUTHOR]

The creation of the periodical domain patterns with a submicron period in lithium niobate on insulator (LNOI) wafers is a key problem for nonlinear-optical applications, including second harmonic generation, backscattering optical parametric oscillator, etc. We have experimentally studied the domain formation and evolution during local polarization reversal in Zþ LNOI wafers with a metal bottom electrode. It has been shown that domain growth occurs by the formation of the spikes at the charged domain wall (CDW). The complicated shape of isolated domains with a jagged CDW has been revealed. The obtained weak domain-domain interaction has been attributed to effective bulk screening by charge injection. The revealed dependence of the domain sizes on humidity caused by the adsorbed water layer should be taken into account during periodical poling. [ABSTRACT FROM AUTHOR]

We report on a compensation characteristic of the phase shifts, originating from the cavity detuning and phase mismatching, in the process of squeezed state generation. In the experiment, the maximum level of squeezing was not generated under coresonance in a doubly resonant optical parametric oscillator (OPO), which was theoretically explained based on the motion equation of the OPO. Furthermore, the power dependence of the squeezing and antisqueezing was also measured at the coresonance and the optimum noise reduction status. The results revalidated the compensation mechanism. Finally, the amplitude quadrature (or vacuum) noise reduction was raised to 11.7 dB (or 12.3 dB) at 8 MHz by finely tuning the crystal temperature away from coresonance. [ABSTRACT FROM AUTHOR]

We demonstrate antenna-coupled spintronic terahertz (THz) emitters excited by 1550 nm, 90 fs laser pulses. Antennas are employed to optimize THz outcoupling and frequency coverage of ferromagnetic/nonmagnetic metallic spintronic structures. We directly compare the antenna-coupled devices to those without antennas. Using a 200 μm H-dipole antenna and an ErAs:InGaAs photoconductive receiver, we obtain a 2.42-fold larger THz peak-peak signal, a bandwidth of 4.5 THz, and an increase in the peak dynamic range (DNR) from 53 dB to 65 dB. A 25 μm slotline antenna offered 5 dB larger peak DNR and a bandwidth of 5 THz. For all measurements, we use a comparatively low laser power of 45 mW from a commercial fiber-coupled system that is frequently employed in table-top THz time-domain systems. [ABSTRACT FROM AUTHOR]

The quantum revolution of the 20th century culminated in the development of quantum optics and the study of nonclassical light. By the beginning of this century, scientific laboratories could produce and handle various quantum states of light: from single photons and photon pairs to squeezed states and bright twin beams. Although only the visible photons are evaluated directly, the team are able to infer correlations with THz photons through a Kirchhoff-Klyshko analysis. As long as quantum sensing relies on relatively weak streams of photons generated by nonlinear crystals, it equally leans on detector technologies that must be sensitive to isolated photons. [Extracted from the article]

Manipulating operation states of coupled spin-torque nano-oscillators (STNOs), including their synchronization, is essential for applications such as complex oscillator networks. In this work, we experimentally demonstrate selective control of two coupled vortex STNOs through microwaveassisted switching of their vortex core polarities. First, the two oscillators are shown to synchronize due to the dipolar interaction in a broad frequency range tuned by an external biasing field. Coherent output is demonstrated along with strong linewidth reduction. Then, we show individual vortex polarity control of each oscillator, which leads to synchronization/desynchronization due to accompanied frequency shift. Our methods can be easily extended to multiple-element coupled oscillator networks. [ABSTRACT FROM AUTHOR]

In this work, we introduce and experimentally demonstrate a parametric phase noise suppression technique, which we call "parametric phase noise filtering." This technique is based on the use of a solid-state parametric amplifier operating in its instability region and included in a non-autonomous feedback loop connected at the output of a noisy oscillator.We demonstrate that such a system behaves as a parametrically driven Duffing resonator and can operate at special points where it becomes largely immune to the phase fluctuations that affect the oscillator output signal. A prototype of a parametric phase noise filter (PFIL) was designed and fabricated to operate in the very-high-frequency range. The PFIL prototype allowed us to significantly reduce the phase noise at the output of a commercial signal generator operating around 220 MHz. Noise reduction of 16 dB (40×) and 13 dB (20×) were obtained, respectively, at 1 and 10 kHz offsets from the carrier frequency. The demonstration of this phase noise suppression technique opens up scenarios in the development of passive and low-cost phase noise cancellation circuits for any application demanding high quality frequency generation. [ABSTRACT FROM AUTHOR]

As important members of nonclassical states of light, squeezed states and entangled states are basic resources for realizing quantum measurements and constructing quantum information networks. We experimentally demonstrate that the two types of nonclassical optical states can be generated from an optical parametric oscillator (OPO) involving a periodically poled KTiOPO4 crystal with a domain-inversion period of 51.7 μm, by changing the polarization of the pump laser. When a vertically polarized 671 nm laser is used to pump the OPO, the intra-cavity frequency-down-conversion with type-0 quasi-phase matching is realized and the output optical beam is a quadrature amplitude squeezed state of light at the wavelength of 1342 nm with the fluctuation of quadrature component of 3.17 dB below the quantum noise limit (QNL). If the pump laser is horizontally polarized, the condition of the type-II quasi-phase matching is satisfied and the output optical beam becomes Einstein-Podolsky-Rosen entangled state of light with correlation variances of both quadrature amplitude-sum and quadrature phase-difference of 2.2 dB below the corresponding QNL. [ABSTRACT FROM AUTHOR]

Intravascular photoacoustic imaging at 1.7 μm spectral band has shown promising capabilities for lipid-rich vulnerable atherosclerotic plaque detection. In this work, we report a high speed catheterbased integrated intravascular photoacoustic/intravascular ultrasound (IVPA/IVUS) imaging system with a 500 Hz optical parametric oscillator laser at 1725 nm. A lipid-mimicking phantom and atherosclerotic rabbit abdominal aorta were imaged at 1 frame per second, which is two orders of magnitude faster than previously reported in IVPA imaging with the same wavelength. Clear photoacoustic signals by the absorption of lipid rich deposition demonstrated the ability of the system for high speed vulnerable atherosclerotic plaques detection. [ABSTRACT FROM AUTHOR]

Using an optical parametric oscillation laser as the excitation source, the dependence of the saturable absorption of multiple-layer graphene upon photon energy is investigated and, in all cases, the saturation intensity is lower for lower excitation photon energy. This result experimentally proves the hourglass shape of the energy band of graphene, which is a well-known theoretical deduction from first principles. The modulation depth increases from 1.5% to 5.1% when the layer number increases from a monolayer to 5-7 layers and, at the same time, the saturation intensity decreases with increasing number of layers. The results demonstrate that, as a saturable absorber of a pulsed laser, graphene can more easily achieve optical modulation in the low energy region, i.e., the infrared waveband. [ABSTRACT FROM AUTHOR]

Spectrally broad frequency comb generation over 510-555 nm range was reported on chirped quasi-phase-matching (QPM) χ(2) nonlinear photonic crystals of 12 mm length with periodicity stepwise increased from 5.9 μm to 7.1 μm. When pumped with nanosecond infrared (IR) frequency comb derived from a QPM optical parametric oscillator (OPO) and spanned over 1040 nm to 1090 nm wavelength range, the 520 nm to 545 nm up-converted green spectra were shown to consist of contributions from (a) second-harmonic generation among the signal or the idler modes, and (b) sum-frequency generation (SFG) from the neighboring pairs of the signal or the idler modes. These mechanisms led the up-converted green frequency comb to have the same mode spacing of 450 GHz as that in the IR-OPO pump comb. As the pump was further detuned from the aforementioned near-degeneracy point and moved toward the signal (1020-1040 nm) and the idler (1090-1110 nm) spectral range, the above QPM parametric processes were preserved in the chirped QPM devices to support up-converted green generation in the 510-520 nm and the 545-555 nm spectral regime. Additional 530-535 nm green spectral generation was also observed due to concurrence of multi-wavelength SFG processes between the (signal, idler) mode pairs. These mechanisms facilitate the chirped QPM device to support a single-pass up-conversion efficiency ~10% when subject to an IR-OPO pump comb with 200 mW average power operated near- or off- the degeneracy point. [ABSTRACT FROM AUTHOR]

We investigate stretching-induced microscopic deformations spatially distributed in a flexible plate of polydimethylsiloxane (PDMS) and their applications in the broadening of the output spectrum of a femtosecond optical parametric oscillator. The hologram of the stretched PDMS plate was used to evaluate indirectly the microscopic deformations. The experimental results show that these deformations exhibit weak scattering and diffraction of light and induce negligible cavity loss, ensuring practical applications of the PDMS plate as an intracavity device for lasers. In combination with the thickness reduction of the PDMS plate through stretching, the distributed deformations enable smooth tuning of the output spectrum. [ABSTRACT FROM AUTHOR]

We demonstrate a near-infrared integrated optical parametric oscillator (OPO) in a direct gap semiconductor. Based on a selectively oxidized GaAs/AlGaAs waveguide and monolithic SiO2/TiO2 dichroic Bragg mirrors, this device combines a strong non-resonant quadratic nonlinearity and form-birefringent type-I phase matching. With a TM00 pump around 1 μm and TE00 signal and idler around 2 μm in a single-pass-pump doubly resonant scheme, we observe an oscillation threshold of 210 mW at degeneracy in the continuous-wave regime. This result represents a significant milestone in the perspective of an electrically injected OPO on chip. [ABSTRACT FROM AUTHOR]

We report an experimental study on widely tunable terahertz (THz) wave difference frequency generation (DFG) with hydrogen-bonded crystals 2-(3-(4-hydroxystyryl)-5,5-dime-thylcyclohex-2-enylidene) malononitrile (OH1). The organic crystals were pumped by a ~1.3 µm double-pass KTiOPO4optical parametric oscillator. A tuning range of 0.02-20 THz was achieved. OH1 crystals offer a long effective interaction length (also high output) for the generation below 3 THz, owing to the low absorption and favorable phase-matching. The highest energy of 507 nJ/pulse was generated at 1.92 THz with a 1.89-mm-thick crystal. Comprehensive explanations were provided, on the basis of theoretical calculations. Cascading phenomenon during the DFG process was demonstrated. The photon conversion efficiency could reach 2.9%. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate self-established noncollinear interactions in a quasi-phase-matched mirrorless optical parametric oscillator using a periodically-poled KTiOPO4 crystal with submicrometer periodicity. It is shown that the oscillation is established in a very specific geometric configuration where the two possible solutions of the energy and momentum conservation conditions become spatially degenerate and contribute coherently to the gain. In this configuration, the signal and the idler remain mutually counter-propagating. The tuning capabilities of a noncollinear mirrorless optical parametric oscillator are investigated. [ABSTRACT FROM AUTHOR]

NO2 molecular tagging velocimetry (MTV) is demonstrated at repetition rates as high as 500 kHz in a laboratory scale Mach 5 wind tunnel. A pulse burst laser and a home built optical parametric oscillator system were used to simultaneously generate the required 355 and 226 nm wavelengths for NO2 photodissociation (tagging) and NO planar laser induced fluorescence imaging (interrogation), respectively. NO2 MTV images were obtained both in front and behind the characteristic bow shock from a 5 mm diameter cylinder. From Gaussian curve fitting, an average free stream flow velocity of 719 m/s was obtained. Absolute statistical precision in velocity of ∼11.5 m/s was determined, corresponding to relative precision of 1.6%-5%, depending upon the region of the flow probed. © 2010 American Institute of Physics [ABSTRACT FROM AUTHOR]

We present an experimental demonstration of simultaneous above-threshold oscillations of the Stokes and anti-Stokes fields together with the single pumping beam with rubidium atoms inside an optical standing-wave cavity. The triple resonant conditions can be achieved easily by making use of the large dispersions due to two-photon transitions in the three-level atomic system. This work provides a way to achieve high efficient nonlinear frequency conversion and the generated bright Stokes and anti-Stokes cavity output beams are potential resource for applications in quantum information science. [ABSTRACT FROM AUTHOR]

We report the direct proof of parametric amplification in a semiconductor waveguide. Thanks to low propagation losses and high nonlinear efficiency, we amplified an input signal at 2 μm in a selectively oxidized GaAs/AlAs multilayer waveguide through the down conversion of a pump at 1 μm. The 4.5% single-pass gain measured for a 30 mW cw pump is compatible with parametric oscillation, provided that distributed and concentrated waveguide losses are further reduced. [ABSTRACT FROM AUTHOR]

We propose a fiber-based system aimed at generating radially and azimuthally polarized beams over spectral ranges of several tens of nanometers. The device is either adaptable to polychromatic sources such as supercontinuum fiber lasers or to tunable ones (optical parametric oscillator, laser diode, etc.). A preliminary version of the system has been engineered to work in the visible portion of the spectrum. The concept proposed here can be adapted to the infrared or blue-UV spectral domains. As a starting application, polychromatic Bessel beams of the first order have been produced. [ABSTRACT FROM AUTHOR]

A synchronously pumped femtosecond optical parametric oscillator (OPO) with intracavity sum frequency generation in a single, periodically poled MgO-doped LiNbO3 (MgO:PPLN) is reported. The used MgO:PPLN crystal contains in series two sections with different poling periods. The first section which generates the 2.5 μm OPO idler wave is followed by a second section which generates the sum frequency of the pump and the idler radiation and thus provides at 589 nm yellow 140 fs long pulses with an average power of up to 190 mW. This corresponds to an optical overall conversion efficiency of 15%. [ABSTRACT FROM AUTHOR]

We present a single-resonant optical parametric oscillator pumped far below threshold as a source for narrow-band single photons. Spontaneous generation of single photons via parametric downconversion is modified and follows the cavity transfer function. Cross-correlation measurements between signal and idler beams show a cavity bandwidth of 62 MHz. As the main improvement to prior realizations, our cavity is locked to the pump beam via the Hänsch-Couillaud method and therefore allows the continuous generation of heralded single photons with long-term stability. [ABSTRACT FROM AUTHOR]

We report an experimental demonstration of optical parametric generation in a periodically poled KTiOPO4 crystal based on the principle of mirrorless optical parametric oscillation. A femtosecond pump pulse spectrally centered at 792 nm from a Ti:sapphire amplifier is prechirped to minimize Kerr effects. The pump pulse is then injected into the nonlinear crystal and down converted to signal and idler pulses, approximately centered at 1584 nm, via amplified spontaneous parametric down conversion in a copropagating type-II quasiphase matching configuration. The maximum internal downconversion efficiency is 43%, the highest ever reported for optical parametric generators based on KTiOPO4 crystals. Such a device may find applications in optical signal processing and biological imaging. [ABSTRACT FROM AUTHOR]

The authors have demonstrated defect mode lasing emission from a spin-coated double-layered dye-doped polymeric cholesteric liquid crystal (PCLC) films with a thin rubbed isotropic layer in between. The rubbed layer acts not only as an alignment layer for the second PCLC layer but also as an isotropic defect layer breaking periodicity of PCLC films. All the processes can be achieved in a wet process. Because of the process, the present polymeric solid-state laser is available as a freestanding thin film of only 5.5 μm in thickness and an almost limitless large area, which enable one to use it as a disposable laser chip of any shapes. [ABSTRACT FROM AUTHOR]

An efficient, widely tunable, narrow-bandwidth, green-pumped, noncritical phase-matched lithium triborate based optical parametric oscillator (OPO) is applied to coherent anti-Stokes Raman scattering (CARS) spectroscopy and microscopy. The tunable signal beam (740–930 nm) of the OPO is combined with the fundamental of a Nd:YVO4 pump laser (1064 nm, 15 ps) to obtain high resolution vibrational spectra of molecules around the CH vibrational stretch (2700–3100 cm-1). The straightforward and convenient tunability of the OPO is demonstrated by CARS microscopy for the identification of different polymer microparticles on the same substrate. [ABSTRACT FROM AUTHOR]

The authors have demonstrated the second-harmonic generation (SHG) in optical channel waveguides which were fabricated in periodically poled lithium niobate (PPLN) by tightly focused femtosecond laser (781 nm) pulses. The measured quasi-phase-matched wavelength and 3 dB bandwidth for SHG in a 44.8-mm-long PPLN waveguide which has a domain period of 16.6 μm were about 1563 and 0.25 nm, respectively. The value of the index difference between the fundamental and harmonic wavelengths in laser written waveguide was inferred to be 0.047. [ABSTRACT FROM AUTHOR]

Electric field distribution in channel of pentacene field effect transistor (FET) was successfully probed by microscopic optical second-harmonic generation (SHG) observation. Microspot SHG signals were acquired at various points in the channel with scanning a spot position along source-drain direction. For the FET at off state, enhanced SHG signal was observed, indicating the Laplace field formation reflecting the device geometry. This clearly supports the insulating nature of pentacene layer at off state. After turning on the FET, SHG profile changed drastically, indicating change in the field distribution by the space charge formation in the channel due to the carrier injection. [ABSTRACT FROM AUTHOR]

The authors observed -7.2±0.2 dB quadrature squeezing at 860 nm by using a subthreshold continuous-wave pumped optical parametric oscillator with a periodically poled KTiOPO4 crystal as a nonlinear optical medium. The squeezing level was measured with the phase of homodyne detection locked at the quadrature. The blue light induced infrared absorption was not observed in the experiment. [ABSTRACT FROM AUTHOR]

The authors observed -7.2±0.2 dB quadrature squeezing at 860 nm by using a subthreshold continuous-wave pumped optical parametric oscillator with a periodically poled KTiOPO4 crystal as a nonlinear optical medium. The squeezing level was measured with the phase of homodyne detection locked at the quadrature. The blue light induced infrared absorption was not observed in the experiment. [ABSTRACT FROM AUTHOR]

We report the dispersion of the optical Kerr effect and the wavelength-dependent critical power of light self-focusing for semiconductors CdxHg1-xGa2S4 in view of the calculated results from the density functional theory combined with an anharmonic oscillator model. It is shown that the third-order optical properties are controlled by the band gaps or cation contents of CdxHg1-xGa2S4, and it is indicated that the optical Kerr effect decreases and the critical power of light self-focusing increases as the x contents and band gaps increase for CdxHg1-xGa2S4. [ABSTRACT FROM AUTHOR]

We report the dispersion of the optical Kerr effect and the wavelength-dependent critical power of light self-focusing for semiconductors CdxHg1-xGa2S4 in view of the calculated results from the density functional theory combined with an anharmonic oscillator model. It is shown that the third-order optical properties are controlled by the band gaps or cation contents of CdxHg1-xGa2S4, and it is indicated that the optical Kerr effect decreases and the critical power of light self-focusing increases as the x contents and band gaps increase for CdxHg1-xGa2S4. [ABSTRACT FROM AUTHOR]

We report the first operation of an optical parametric oscillator in a chalcopyrite crystal, AgGaS2. Tuning from 1.4 to 4.0 μm is demonstrated for 1.06-μm Nd:yttrium aluminum garnet pumping. The potential tuning range extends to the 12-μm transparency limit of the crystal. [ABSTRACT FROM AUTHOR]

Intense line radiation from plasmas of Mn VI, P IX, Al V, Al VIII, Al IX, and Al XI may be used to selectively pump population inversions in plasmas of C III, N IV, F VI, Ne VII, Na VIII, and Mg IX. Quasi-cw lasing is possible on 4p-3d and 4f-3d transitions at wavelengths 2177 -230 Å. At the extreme ultraviolet wavelengths, 1-J, 10-ns laser output pulses at 108 W power levels are shown possible with existing discharge and laser technology. [ABSTRACT FROM AUTHOR]

We propose nonuniform structures of phase-locked diode lasers, which make it possible to discriminate efficiently against all the higher order array supermodes (lateral modes). In these nonuniform arrays, the effective mode index in each channel varies across the array. Consequently, the envelopes of the various supermodes, including the highest order one, differ significantly from each other. Thus, by proper tailoring of the gain distribution across the array, one can conveniently select the fundamental supermode. Such fundamental supermode oscillation is essential in order to obtain single lobe, diffraction limited beams and minimal spectral spread from phase-locked laser arrays. [ABSTRACT FROM AUTHOR]

A cw CO2 laser operating on the R(30) 9-μm transition is down shifted by 180 MHz in a pair of acousto-optic modulators, and used to optically pump sR(5,0) transition of NH3 at line center. Vibrational inversion is created in the ν2 mode, and cw oscillation is observed on 20 different NH3 lines, spanning the region between 10.7 and 13.3 μm. Single line output powers as high as 760 mW were measured in a waveguide cavity. The operation of this laser is explained using a simple thermalization model, and several potential applications are discussed. [ABSTRACT FROM AUTHOR]

The operation of the first optical parametric oscillator using a urea crystal is reported. Tunable radiation in both the visible and IR was obtained with conversion efficiencies as high as 20%. [ABSTRACT FROM AUTHOR]

We report the improvement of the amplified spontaneous emission (ASE) performance in the optically pumped symmetric thin film waveguide glass/indium-tin oxide (ITO)/SiO2/poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene]/SiO2/Al or Ag by optimizing the thickness of SiO2 and replacing the Al electrode with Ag, where SiO2 acted as a spacer layer to prevent the ASE at 620 nm from being destructed. The results show that the SiO2/Ag cladding reduced the ASE threshold to 4 μJ/pulse compared with the SiO2/Al cladding, owing to the higher work function and reflection rate as well as lower absorption loss of the Ag electrode. No photoluminescence at 580 nm being observed makes it possible for an electric field to only modulate the ASE at 620 nm in the device with the SiO2/Ag cladding. The electric-field quenching of the ASE has been observed, which increases with the electric field. The field dependence of ASE can be attributed to field-induced dissociation of photogenerated excitons in the polymer waveguides. [ABSTRACT FROM AUTHOR]

We report the design and experimental results of a two chip co-linear T-cavity vertical external cavity surface emitting laser (VECSEL) capable of generating two continuously tunable orthogonally polarized lasing wavelengths. A polarizing beamsplitter is used to overlap two VECSEL cavities thus generating high-power intra-cavity two-wavelength generation ideal for type-II nonlinear frequency conversion. Nearly equal power at each wavelength with a combined dual-wavelength CW output power in excess of 13 W was observed. In a high Q cavity, the wavelength separation was tuned from 35 nm to 52 nm by using birefringent filters in regions where each wavelength lases independently of the other. [ABSTRACT FROM AUTHOR]

We investigate the effect of angular tuning on coherently coupled optical parametric generation (OPG) in two-dimensional purely nonlinear lattices and demonstrate how it allows accessing both shared signal and shared idler regimes, resulting in twin-beam outputs in the mid- and near infrared, respectively. Furthermore, we present the results of a systematic spectral and angular mapping of the twin-beam OPG response in the near-infrared as a function of the pump incidence angle. [ABSTRACT FROM AUTHOR]