Modified spectrum autointerferometric correlation (MOSAIC) for single-shot pulse characterization

A method for generation of the modified spectrum autointerferometric correlation that allows single-shot pulse characterization is demonstrated. A sensitive graphical representation of the ultrashort pulse phase quality is introduced that delineates the difference between the presence of temporal and spectral phase distortions. Using these schemes, full-field reconstruction of ultrashort laser pulses is obtained in real time using an efficient iterative technique. (a) Single-shot characterization using a combination of fringe-free (noninterferometric) autocorrelation and second-harmonic spectrum (b) A hybrid graphical representation that distinguishes between spectral and temporal phase distortions (c) Real-time full-field reconstruction using the above schemes with an efficient sequential search algorithm Naganuma et al. showed that the pulse spectrum and IAC provide a sufficient dataset to uniquely reconstruct the complex electric field, with only a timedirection ambiguity The increased SNR found on averaged MOSAIC traces extends the utility of all retrieval techniques using the dataset outlined by Naganuma et al. The principle of computing a MOSAIC can be described in the frequency domain as follows: a secondorder IAC waveform with a fringe frequency ⍀ is Fourier transformed to generate a spectrum. Spectral filtering is then performed to remove the ⍀ component and amplify the 2⍀ component by a factor of 2. An inverse Fourier transform generates a new time-domain signal known as a fringe-resolved MOSAIC In the (delay) time-domain analysis, the maximum and minimum envelopes of MOSAIC are given by the intensity autocorrelation, g͑͒ = ͐f͑t͒f͑t + ͒dt, and the difference computation, S min = g͑͒ − ͉g p ͉͑͒, respectivel

All-Optical Switching Devices Based On Large Nonlinear Phase-Shifts From 2Nd Harmonic-Generation

We show that the large nonlinear phase shifts obtained from phase-mismatched second harmonic generation can be used to implement all-optical switching devices such as a nonlinear Mach-Zehnder interferometer and a nonlinear directional coupler

Precise Determination of Minimum Achievable Temperature for Solid-State Optical Refrigeration

We measure the minimum achievable temperature (MAT) as a function of excitation wavelength in anti-Stokes fluorescence cooling of high purity Yb3+-doped LiYF4 (Yb:YLF) crystal. Such measurements were obtained by developing a sensitive noncontact thermometry that is based on a two-band differential luminescence spectroscopy using balanced photo-detectors. These measurements are in excellent agreement with the prediction of the laser cooling model and identify MAT of 110 K at 1020 nm, corresponding to E4-E5 Stark manifold transition in Yb:YLF crystal.Comment: 10 pages, 6 figure

Anti-Stokes luminescence cooling of Tm3+ doped BaY2F8

We report laser-induced cooling with thulium-doped BaY2F8 single crystals grown using the Czochralski technique. The spectroscopic characterization of the crystals has been used to evaluate the laser cooling performance of the samples. Cooling by 3 degrees below ambient temperature is obtained in a single-pass geometry with 4.4 Watts of pump laser power at lambda = 1855 nm

Tm-doped Crystals for mid-IR Optical Cryocoolers and Radiation Balanced Lasers

We report the complete characterization of various cooling grade Tm-doped crystals including the first demonstration of optical refrigeration in Tm:YLF crystals. Room temperature laser cooling efficiencies of 1% and 2% (mol) Tm:YLF, and 1% Tm:BYF crystals at different excitation polarizations are measured and their external quantum efficiency and background absorption are extracted. By performing detailed low-temperature spectroscopic analysis of the samples, global minimum achievable temperatures of 160 K to 110 K are estimated. The potential of Tm-doped crystals to realize mid-IR optical cryocoolers and radiation balanced lasers (RBLs) in the eye-safe region of the spectrum is discussed, and a promising 2-tone RBL in a tandem structure of Tm:YLF and Ho:YLF crystals is proposed.Comment: References were updated. (4 pages, 5 figures

Synthesis and evaluation of ultra-pure rare-earth-coped glass for laser refrigeration

Significant progress has been made in synthesizing and characterizing ultra-pure, rare-earth doped ZIBLAN (ZrF{sub 4}-InF{sub 3}BaF{sub 2}-LaF{sub 3}-AlF{sub 3}-NaF) glass capable of laser refrigeration. The glass was produced from fluorides which were purified and subsequently treated with hydrofluoric gas at elevated temperatures to remove impurities before glass formation. Several Yb3 +-doped samples were studied with degrees of purity and composition with successive iterations producing an improved material. We have developed a non-invasive, spectroscopic technique, two band differential luminescence thermometry (TBDLT), to evaluate the intrinsic quality of the ytterbium doped ZIBLAN used for laser cooling experiments. TBDLT measures local temperature changes within an illuminated volume resulting solely from changes in the relative thermal population of the excited state levels. This TBDLT technique utilizes two commercially available band pass filters to select and integrate the 'difference regions' of interest in the luminescence spectra. The goal is to determine the minimum temperature to which the ytterbium sample can cool on the local scale, unphased by surface heating. This temperature where heating and cooling are exactly balanced is the zero crossing temperature (ZCT) and can be used as a measure for the presence of impurities and the overall quality of the laser cooling material. Overall, favorable results were obtained from 1 % Yb3+-doped glass, indicating our glasses are desirable for laser refrigeration