Publications by authors named "Kevin T Zawilski"

13 Publications

  • Page 1 of 1

Terahertz generation by optical rectification in chalcopyrite crystals ZnGeP, CdGeP and CdSiP.

Opt Express 2019 Jun;27(12):16958-16965

Optical rectification of near-infrared laser pulses generates broadband terahertz radiation in chalcopyrite crystals CdGeP, ZnGeP and CdSiP. The emission is characterized using linear-polarized excitation from 0.8 eV to 1.55 eV (1550 nm - 800 nm). All three crystals are (110)-cut and polished to 0.5 mm, thinner than the coherence length across most of the excitation photon energy range, such that they all produce a bandwidth ~2.5 THz when excited with ~100 fs pulses. It is found that CdGeP produced the strongest emission at telecoms wavelengths, while CdSiP is generally the strongest source. Pump-intensity dependence provides the nonlinear coefficients for each crystal.
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http://dx.doi.org/10.1364/OE.27.016958DOI Listing
June 2019

Continuous-wave whispering-gallery optical parametric oscillator based on CdSiP.

Opt Express 2018 Apr;26(8):10833-10841

Continuous-wave (cw) optical parametric oscillators (OPOs) are ideally suited for applications, for example high-resolution spectroscopy, that need coherent sources combining narrow-linewidth emission with good wavelength tunability. Here, we demonstrate for the first time cw OPOs based on a millimeter-sized whispering gallery resonator (WGR) made of cadmium silicon phosphide (CdSiP). By employing a compact laser diode at 1.57-μm wavelength for pumping, a cw OPO with wavelength tunability from 2.3 μm to 5.1 μm is realized based on such a resonator. The oscillation thresholds are in the milliwatt range. The maximum total power conversion efficiency reaches more than 15%. The intrinsic quality factor at 1.57 μm is determined to be 3.5 × 10. This work suggests that CdSiP is a very promising alternative for constructing mid-infrared parametric devices.
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http://dx.doi.org/10.1364/OE.26.010833DOI Listing
April 2018

Multi-watt, multi-octave, mid-infrared femtosecond source.

Sci Adv 2018 04 20;4(4):eaaq1526. Epub 2018 Apr 20.

Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching, Germany.

Spectroscopy in the wavelength range from 2 to 11 μm (900 to 5000 cm) implies a multitude of applications in fundamental physics, chemistry, as well as environmental and life sciences. The related vibrational transitions, which all infrared-active small molecules, the most common functional groups, as well as biomolecules like proteins, lipids, nucleic acids, and carbohydrates exhibit, reveal information about molecular structure and composition. However, light sources and detectors in the mid-infrared have been inferior to those in the visible or near-infrared, in terms of power, bandwidth, and sensitivity, severely limiting the performance of infrared experimental techniques. This article demonstrates the generation of femtosecond radiation with up to 5 W at 4.1 μm and 1.3 W at 8.5 μm, corresponding to an order-of-magnitude average power increase for ultrafast light sources operating at wavelengths longer than 5 μm. The presented concept is based on power-scalable near-infrared lasers emitting at a wavelength near 1 μm, which pump optical parametric amplifiers. In addition, both wavelength tunability and supercontinuum generation are reported, resulting in spectral coverage from 1.6 to 10.2 μm with power densities exceeding state-of-the-art synchrotron sources over the entire range. The flexible frequency conversion scheme is highly attractive for both up-conversion and frequency comb spectroscopy, as well as for a variety of time-domain applications.
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http://dx.doi.org/10.1126/sciadv.aaq1526DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5917893PMC
April 2018

Compact and efficient mid-IR OPO source pumped by a passively Q-switched Tm:YAP laser.

Opt Lett 2018 Mar;43(5):1099-1102

We describe a compact and efficient mid-infrared (mid-IR) source based on zinc germanium phosphide (ZGP) and cadmium silicon phosphide (CSP) optical parametric oscillators (OPOs), operating in near degenerate condition, directly pumped by a 1.94 μm thulium (Tm)-doped yttrium-aluminum-perovskite (YAP) laser. The Tm:YAP laser is passively Q-switched by a chromium-doped zinc sulfide saturable absorber, and is operated to 4 W average power with a peak power of 29 kW. The laser emission was used to pump CSP and ZGP doubly resonant linear OPO cavities, generating a maximum 3.5-4.2 μm mid-IR emission of 2.5 W for CSP and 2.3 W for ZGP, with maximum optical conversion efficiencies of 65% and 58%, respectively, achieved for the two OPO crystals.
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http://dx.doi.org/10.1364/OL.43.001099DOI Listing
March 2018

Femtosecond-laser pumped CdSiP₂ optical parametric oscillator producing 100 MHz pulses centered at 6.2 μm.

Opt Lett 2013 Dec;38(23):5110-3

We report the first, to the best of our knowledge, femtosecond-laser-pumped optical parametric oscillator (OPO) based on the newly developed nonlinear crystal, CdSiP₂. The OPO was synchronously pumped by a mode-locked Yb:KYW/Yb:fiber master-oscillator power amplifier, providing 1.053 μm pump pulses with durations of 130 fs at a repetition rate of 100 MHz. The 0.5-mm-thick CdSiP₂ crystal was cut for a type-I noncritical interaction, providing a broad phase-matching bandwidth and ensuring excellent temporal overlap among the pump, signal, and idler pulses. The OPO generated signal pulses with a spectral coverage over 1260-1310 nm and mid-infrared idler pulses with a broad spectral coverage at 5.8-6.6 μm (6.2 THz). With a 2% output coupler (OC), the threshold pump power was 600 mW. At the maximum pump power of 1.6 W, 0.55 W was absorbed due to two-photon absorption and residual linear absorption in the CdSiP₂ crystal, 0.75 W was transmitted, and 53 mW signal power was extracted through the OC. We estimate that the generated idler power was 24 mW.
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http://dx.doi.org/10.1364/OL.38.005110DOI Listing
December 2013

Narrow-bandwidth, ~100 ps seeded optical parametric generation in CdSiP2 pumped by Raman-shifted pulses at 1198 nm.

Opt Lett 2013 Sep;38(17):3344-6

Max-Born-Institute for Nonlinear Optics and Ultrafast Spectroscopy, Berlin, Germany.

Low-threshold, efficient optical parametric generation at ~4.64 μm is demonstrated using CdSiP2 nonlinear crystal pumped by 150 ps Raman shifted pump pulses at 1198 nm in noncritical configuration at 1 kHz repetition rate. Maximum single pulse idler energy of 6 μJ and total conversion efficiency of 30% are achieved. Seeding at the signal wavelength with a distributed feedback laser diode enables ~25 fold narrowing of the bandwidths down to ~10 GHz, resulting in a Fourier product of ~1 for the ~100 ps long signal (1615 nm) and idler (4.64 μm) pulses.
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http://dx.doi.org/10.1364/OL.38.003344DOI Listing
September 2013

Narrow-bandwidth, mid-infrared, seeded optical parametric generation in 90° phase-matched CdSiP2 crystal pumped by diffraction limited 500 ps pulses at 1064 nm.

Opt Lett 2012 Aug;37(15):3219-21

Max-Born-Institute for Nonlinear Optics and Ultrafast Spectroscopy, Berlin, Germany.

Low-threshold, efficient optical parametric generation at ~6100 nm is demonstrated using CdSiP2 nonlinear crystal at 1 to 10 kHz repetition rates with relatively long 500 ps pump pulses at 1064 nm. Maximum single pulse energy of 8.7 μJ and average power of 79 mW are achieved for the idler. Seeding at the signal wavelength is employed using a distributed feedback laser diode, which enables approximately tenfold narrowing of the idler bandwidth down to less than 1 nm.
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http://dx.doi.org/10.1364/OL.37.003219DOI Listing
August 2012

Optical parametric generation in CdSiP2 at 6.125 μm pumped by 8 ns long pulses at 1064 nm.

Opt Lett 2012 Feb;37(4):740-2

Max-Born-Institute for Nonlinear Optics and Ultrafast Spectroscopy, Berlin, Germany.

A 21.4 mm long noncritically cut CdSiP2 crystal, pumped by 8 ns pulses at 1064 nm in a double-pass configuration for pump, signal, and idler, generated 523 μJ, 5.8 ns idler pulses at 6.125 μm. The average power of 52.3 mW at the repetition rate of 100 Hz is the highest ever achieved at such wavelengths with direct down conversion from the 1 μm spectral range.
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http://dx.doi.org/10.1364/OL.37.000740DOI Listing
February 2012

Phase-matching properties and refined Sellmeier equations of the new nonlinear infrared crystal CdSiP2.

Opt Lett 2011 May;36(10):1800-2

Institut Néel Centre National de la Recherche Scientifique - Université Joseph Fourier, 25 Rue des Martyrs, BP 166, F38402 Grenoble Cedex 9, France.

We directly measured the second harmonic generation and difference frequency generation phase-matching directions of the nonlinear crystal CdSiP(2) until 9.5 μm using the sphere method. The simultaneous fit of the experimental angular data allowed the Sellmeier equations of the ordinary and extraordinary principal refractive indices to be refined over the entire transparency range of the crystal.
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http://dx.doi.org/10.1364/OL.36.001800DOI Listing
May 2011

Subnanosecond, 1 kHz, temperature-tuned, noncritical mid-infrared optical parametric oscillator based on CdSiP(2) crystal pumped at 1064 nm.

Opt Lett 2010 Apr;35(8):1230-2

Max-Born-Institute for Nonlinear Optics and Ultrafast Spectroscopy, 2A Max-Born-Str., D-12489 Berlin, Germany.

Operation of an optical parametric oscillator based on CdSiP(2) and pumped at 1064 nm is demonstrated at a repetition rate of 1 kHz. The maximum output idler energy of 24 microJ at 6.125 microm corresponds to an average power of 24 mW. Increasing the crystal temperature up to 150 degrees in the noncritical (90 degrees) configuration leads to idler wavelength tuning from 6.117 to 6.554 microm. Subnanosecond pulse durations are obtained for the signal and idler as a result of the 1 ns pulse duration of the pump, made possible by the rather short crystal and cavity lengths (approximately 1 cm).
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http://dx.doi.org/10.1364/OL.35.001230DOI Listing
April 2010

Noncritical singly resonant synchronously pumped OPO for generation of picosecond pulses in the mid-infrared near 6.4 microm.

Opt Lett 2009 Oct;34(20):3053-5

Centre de Recherche en Physique de la Matière et du Rayonnement (PMR), University of Namur, 61 rue de Bruxelles, B-5000, Namur, Belgium.

The recently developed chalcopyrite CdSiP(2) is employed in a picosecond, 90 degrees -phase-matched, synchronously pumped, optical parametric oscillator pumped at 1064 nm to produce steady-state idler pulses near 6.4 microm with an energy as high as 2.8 microJ at 100 MHz, in a train of 2-micros-long macropulses following at a repetition rate of 25 Hz. Without an intracavity etalon, the 12.6-ps-long micropulses have a spectral width of 240 GHz.
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http://dx.doi.org/10.1364/OL.34.003053DOI Listing
October 2009

Noncritical singly resonant optical parametric oscillator operation near 6.2 microm based on a CdSiP(2) crystal pumped at 1064 nm.

Opt Lett 2009 Aug;34(16):2399-401

Max-Born-Institute for Nonlinear Optics and Ultrafast Spectroscopy, 2A Max-Born-Strasse, D-12489 Berlin, Germany.

CdSiP(2) is employed in a nanosecond, 90 degrees -phase-matched, singly resonant optical parametric oscillator pumped at 1064 nm to produce idler pulses near 6.2 microm with an energy as high as 470 microJ at 10 Hz.
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http://dx.doi.org/10.1364/ol.34.002399DOI Listing
August 2009

Infrared reflectance and photoemission spectroscopy studies across the phase transition boundary in thin film vanadium dioxide.

J Phys Condens Matter 2008 Nov 21;20(46):465204. Epub 2008 Oct 21.

Harvard School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.

Optical properties and valence band density of states near the Fermi level of high-quality VO(2) thin films have been investigated by mid-infrared reflectometry and hard-UV (hν = 150 eV) photoemission spectroscopy. An exceptionally large change in reflectance from 2 to 94% is found upon the thermally driven metal-insulator transition (MIT). The infrared dispersion spectra of the reflectance across the MIT are presented and evidence for the percolative nature of the MIT is pointed out. The discrepancy between the MIT temperatures defined from the electrical and optical properties is found and its origin is discussed. The manifestation of the MIT is observed in the photoemission spectra of the V 3d levels. The analysis of the changes of the V 3d density of states is done and the top valence band shift upon the MIT is measured to be 0.6 eV.
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http://dx.doi.org/10.1088/0953-8984/20/46/465204DOI Listing
November 2008