Noncritical Type Research Articles

Modeling and Optimization of a Community Microgrid Components

The modeling and optimization of a community microgrid situated in an urban area is presented in this paper. Such communities include places like housing estates, large hospital complexes, large residential complexes, and universities of higher learning. The case study used in this work is a housing estate situated in Cape Town, South Africa. Distributed energy resources used in the study are diesel generators, rooftop solar photovoltaic system, and the electrical load that is segmented into critical and non-critical type. The segmentation of the load allows an intelligent load shedding scheme in order to maintain the stability of the overall system. HOMER modeling software environment is used to model and optimize the community microgrid component sizes for technical and economic feasibility. An optional grid-connected mode as a backup energy system is evaluated against the grid-forming mode of the community microgrid system. Simulation results are obtained and discussed. Conclusion of decision-making about using a grid-forming microgrid system or grid-connected-PV is presented.

LiNa5Mo9O30: Crystal Growth, Linear, and Nonlinear Optical Properties

We report on the crystal growth, linear, and nonlinear optical properties of LiNa5Mo9O30. The refractive indices were measured, and a very large birefringence of 0.2545 at 450.2 nm was determined. In addition, calculated phase-matching curves indicate that LiNa5Mo9O30 can achieve noncritical type I and type II phase-matching (NCPM) for incident 1064 nm radiation. Maker fringe measurements, to determine individual nonlinear optical coefficients, were also performed on the crystals resulting in d31 = 1.4 pm/V, d32 = 4.3 pm/V, and d33 = 1.1 pm/V. The laser damage threshold (LDT) is around 1.2 GW/cm2 at 1064 nm using a 6 ns Nd:YAG laser operating at 5 Hz. The quality of the crystals was measured by high resolution X-ray diffraction rocking curve measurements that revealed a full width at half-maximum (fwhm) of 59″ from the (001) reflection. The absorption edge was determined to be 357 nm, with transmission up to 5.26 μm. Our results indicate that single crystal LiNa5Mo9O30 is an excellent polarizer as well as second-order nonlinear optical material.

Nonsupersymmetric Seiberg duality, orientifold QCD, and noncritical strings

We propose an electric-magnetic duality and conjecture an exact conformal window for a class of nonsupersymmetric $U({N}_{c})$ gauge theories with fermions in the (anti)symmetric representation of the gauge group and ${N}_{f}$ additional scalar and fermion flavors. The duality exchanges ${N}_{c}\ensuremath{\rightarrow}{N}_{f}\ensuremath{-}{N}_{c}\ensuremath{\mp}4$ leaving ${N}_{f}$ invariant, and has common features with Seiberg duality in $\mathcal{N}=1$ super QCD (SQCD) with $SU$ or $SO/Sp$ gauge group. At large $N$ the duality holds due to planar equivalence with $\mathcal{N}=1$ SQCD. At finite $N$ we embed these gauge theories in a setup with D-branes and orientifolds in a nonsupersymmetric, but tachyon-free, noncritical type 0B string theory and argue in favor of the duality in terms of boundary and crosscap state monodromies as in analogous supersymmetric situations. One can verify explicitly that the resulting duals have matching global anomalies. Finally, we comment on the moduli space of these gauge theories and discuss other potential nonsupersymmetric examples that could exhibit similar dualities.

Third order frequency generation in TiO2 rutile and KTiOPO4

Third harmonic generation and triple photon generation properties of TiO2 rutile single crystal, including phase-matching and cubic nonlinearity, are studied and compared with KTP. We measured the fundamental wavelength of the angular noncritical type II phase-matched THG, we refined the dispersion equations, and we showed that this crystal has a figure of merit 7.5 times that of KTP.

Unoriented Minimal Type 0 Strings

We define a family of string equations with perturbative expansions that admit an interpretation as an unoriented minimal string theory with background D-branes and R-R fluxes. The theory also has a well-defined non-perturbative sector and we expect it to have a continuum interpretation as an orientifold projection of the non-critical type~0A string for \hat{c}=0, the (2,4) model. There is a second perturbative region which is consistent with an interpretation in terms of background R-R fluxes. We identify a natural parameter in the formulation that we speculate may have an interpretation as characterizing the contribution of a new type of background D-brane. There is a non-perturbative map to a family of string equations which we expect to be the \hat{c}=0 type 0B string. The map exchanges D-branes and R-R fluxes. We present the general structure of the string equations for the (2,4k) type 0A models.

Non-critical supergravity (d> 1) and holography

In this paper we investigate the supergravity equations of motion associated with non-critical ($d>1$) type II string theories that incorporate RR forms. Using a superpotential formalism we determine several classes of solutions. In particular we find analytic backgrounds with a structure of $AdS_{p+2}\times S^{d-p-2}$ and numerical solutions that asymptote a linear dilaton with a topology of $R^{1,d-3}\times R \times S^1$. The SUGRA solutions we have found can serve as anti holographic descriptions of gauge theories in a large $N$ limit which is different than the one of the critical gauge/gravity duality. It is characterized by $N\rt \infty$ and $g_{YM}^2 N \sim 1$. We have made the first steps in analyzing the corresponding gauge theory properties like Wilson loops and the glue-ball spectra.

Single-tone frequency-modulation spectroscopy with frequency-doubled current-modulated diode laser light

We demonstrate and characterize the generation of single-tone frequency-modulated and frequency-doubled radiation at 400 MHz and 430 nm. We obtained the radiation at 430 nm by frequency doubling light from a current-modulated 860-nm diode laser, using noncritical type I phase matching in a KNbO(3) crystal. The optical spectrum of the doubled light was found to be in keeping with our expectations based on the measured frequency- and amplitude-modulation indices of the fundamental radiation. The experimentally measured diode laser and crystal parameters were used to simulate the in-phase and quadrature signals that would be observed in a single-tone frequency-modulation spectroscopy experiment.

Generalised theory describing non-linear interaction of focused Gaussian waves of arbitrary polarisation states

We describe the most general case of optical parametric three-wave interactions considering arbitrarily polarised Gaussian waves with individual focusing parameters. Different combinations of polarisation result in different beam walk-off of the interacting fields, influencing the strength of the coupling. Formulas for all possible combinations of polarisations in a second order nonlinear process are derived and their differences explained. As an example, it is shown that the coupling strength in case of Type II phase-matching in general is in-between the coupling strength of non-critical phase-matching and Type I phase-matching including walk-off, with the exact value depending of the relative wavelength of the interacting fields.

Non-critical type 0 string theories and their field theory duals

In this paper we continue the study of the non-critical type 0 string and its field theory duals. We begin by reviewing some facts and conjectures about these theories. We move on to our proposal for the type 0 effective action in any dimension, its RR fields and their Chern-Simons couplings. We then focus on the case without compact dimensions and study its field theory duals. We show that one can parameterize all dual physical quantities in terms of a finite number of unknown parameters. By making some further assumptions on the tachyon couplings, one can still make some “model independent” statements.

Efficient second-harmonic generation by lens wave-guiding in KNbO3 crystals

A novel configuration of lens waveguiding in a cascade of nonlinear optical crystals is proposed whereby the conversion efficiency increases quadratically with the interaction length. 17 mW of continuous-wave blue light at 428.5 nm and 35 mW at 490.8 nm is generated by noncritical type I phase-matched frequency doubling of near infrared laser diodes in a cascade of two and three potassium niobate (KNbO3) crystals, respectively.

Efficient generation of CW blue light by sum-frequency mixing of laser diodes in KNbO 3

A tunable continuous-wave diode-pumped blue laser is demonstrated by noncritical type I phase-matched sum-frequency generation in a potassium niobate (KNbO 3) crystal. A maximum output power of 65 mW of nearly diffraction-limited light at 434.7 nm is generated in a 14.5 mm long crystal by mixing a 982.6 nm master-oscillator power-amplifier InGaAs laser diode and a 779.5 nm AlGaAs laser diode with an overall conversion efficiency of 7.2%/W. The blue laser is continuously tunable over the wavelength range from 432 to 438 nm.

Picosecond near- to mid-infrared optical parametric oscillator using KTiOAsO4

The operation and characterization of a high-repetition-rate singly-resonant picosecond optical parametric oscillator based on the non-linear material KTiOAsO4 and synchronously pumped by a Kerr-lens-mode-locked Ti:sapphire laser at 81 MHz is described. By utilizing non-critical type II phase-matching in a 10 mm crystal, average near-infrared output powers of 403 mW have been generated at 31% extraction efficiency. The oscillator exhibits a pump power threshold of 230 mW and with the available mirror set can provide signal tuning over 1.116–1.281 μm and idler tuning over 2.260–3.160 μm by tuning the pump wavelength over 770–896 nm. Without dispersion compensation, near-transform-limited signal pulses with durations of 1.01–1.03 ps and idler pulses with 1.61–2.91 ps duration have been obtained for 1.2 ps input pump pulses.

High-power, high-repetition-rate picosecond optical parametric oscillator tunable in the visible

We describe an intracavity frequency-doubled high repetition-rate picosecond optical parametric oscillator for the visible based solely on the nonlinear crystal LiB(3)O(5) and synchronously pumped by a self-mode-locked Ti:sapphire laser. Under temperature-tuned noncritical type I and type II phase matching, average visible output powers of 320 mW have been generated at an 81-MHz repetition rate. With the available mirror set, continuous tuning from 584 to 771 nm is demonstrated for a range of phase-matching temperatures. Transform-limited pulses with durations of 840-880 fs have been obtained across the visible range for pump pulse durations of 1-1.2 ps.

Tunable blue light generation by sum-frequencymixing of AlGaAs and InGaAs laser diodes in KNbO 3

A 25 mW continuous-wave blue laser is demonstrated by noncritical type I phase-matched sum-frequency mixing of a master-oscillator power-amplifier InGaAs laser diode and an AlGaAs laser diode in a potassium niobate (KNbO3) crystal. The blue laser is continuously tunable over the wavelength range from 431 to 438 nm.

High-power, high-repetition-rate picosecond optical parametric oscillator for the near- to mid-infrared

A high-repetition-rate, singly resonant optical parametric oscillator based on KTiOAsO(4) and synchronously pumped by a self-mode-locked Ti:sapphire laser is reported. Under the conditions of pump-tuned noncritical type II phase matching, average near-infrared output powers of 403 mW have been generated at a repetition rate of 81 MHz. With the available mirror set, signal tuning over 1.116-1.281 microm and idler tuning over 2.260-3.160 microm are demonstrated for a range of pump wavelengths. Without dispersion compensation, signal (idler) pulses with durations of 1.01-1.03 (1.61-2.91) ps have been obtained for 1.2-ps input pump pulses.

SHG phase matching conditions for undoped and doped lithium niobate

Abstract We measured the refractive indices of undoped and Zn- or Mg-doped lithium niobate in the wavelength range 400 to 1200 nm. The results are described by a generalized Sellmeier equation which takes into account the defect structure of the material. From the generalized Sellmeier equation a simple relation between the phase matching temperature for noncritical type I second harmonic generation (SHG) and the internal critical phase matching angle is derived. Good correspondence with experimental data over a wide composition and fundamental wavelength range is observed.

Picosecond Ti:sapphire-pumped optical parametric oscillator based on LiB_3O_5

We report a high-repetition-rate, singly resonant optical parametric oscillator based on the nonlinear crystal LiB(3)O(5), which is synchronously pumped by a continuous train of picosecond pulses from a self-mode-locked Ti:sapphire laser. Under temperature-tuned noncritical type I phase matching, total average near-infrared output powers of 90 mW at a repetition rate of 81 MHz have been generated over a signal (idler) tuning range of 1.374-1.530 microm (1.676-1.828 microm). Without dispersion compensation, transform-limited signal pulses with durations of 520-780 fs have been obtained at 1.2 times threshold for 1.8-ps input pump pulses.

Temperature-tuned noncritically phase-matched picosecond LiB3O5 optical parameter oscillator

Efficient picosecond optical parametric oscillation in LiB3O5 is demonstrated using ∼55 ps pump pulses at 523.5 nm, obtained from a frequency-doubled, mode-locked, Q-switched, diode-laser-pumped Nd:YLF laser. By exploiting temperature tuning under noncritical type I phase matching, continuously tunable radiation over the range 0.909–1.235 μm has been generated at external power conversion efficiencies approaching 50%. The oscillator has a pump power threshold of 4.5 mW, corresponding to a Q-switched pulse energy of 9 μJ, and can provide a total average output power of 8 mW at 500 Hz, in pulses of ∼33 ps duration. At five times above threshold, the internal pump depletion of the oscillator was 54%.

Broadband squeezing of light by pulse excitation

Broadband squeezed states of the electromagnetic field are generated by degenerate parametric downconversion with pulse-light excitation in a Ba(2)NaNb(5)O(15) crystal, in which noncritical type I phase matching is attained. Noise reduction below the level of the vacuum fluctuation is clearly observed over a detection bandwidth from dc to approximately 70 MHz. The minimum noise level obtained in the quiet quadrature is 1.1 dB below the shot-noise level. The scheme used in the present experiment is simple and promising for further improvement of squeezing. The relation between squeezing and parametric fluorescence is discussed quantitatively for the first time to the authors' knowledge.

Linear and nonlinear optical properties of 2-cyclooctylamino-5-nitropyridine

Abstract The linear and nonlinear optical properties of 2-cyclooctylamino-5-nitropyridine (COANP) have been investigated. The refractive indices were measured in the visible and the near infrared. The three main refractive indices at λ = 650 nm are na = 1.688, nb = 1.774 and nc = 1.643. The nonlinear optical susceptibilities d 32 = (32 ± 16) pm/V and d 33 = (13.7 ± 2) pm/V were determined. Calculations carried out show interesting critical phase-matching properties (frequency-doubling of the Nd: YAG laser at λ = 1064 nm). Noncritical type I phase-matching is predicted for the fundamental wavelengths λ = 1023 nm and λ = 1413 nm using the nonlinear optical susceptibilities d 32 and d 31 respectively.