Supercontinuum

About: Supercontinuum is a research topic. Over the lifetime, 7071 publications have been published within this topic receiving 127671 citations.

Optical pulse sources

Abstract: An optical pulse source comprising a DPSS pump laser, a photonic crystal fiber (PCF), and acousto-optic modulator (AOM) gating device is disclosed. The pump pulses are coupled through lenses to the AOM gating device, which is synchronized to the pump laser and is operable to gate the pump pulses to a reduced repetition rate Rr=Rf/N, where Rf is the pump laser fundamental frequency. The pulses from the AOM are injected via optics into the PCF. Propagation through the PCF causes the pulses to broaden spectrally to produce optical supercontinuum pulses. An optical pulse source that further includes an acousto-optical tunable filter (AOTF) operable to convert the optical supercontinuum pulses into wavelength variable output pulses is also provided. A method of scaling the energy of the optical supercontinuum pulses is also disclosed.

Trace species detection in the near infrared using Fourier transform broadband cavity enhanced absorption spectroscopy: initial studies on potential breath analytes.

Abstract: Cavity enhanced absorption measurements have been made of several species that absorb light between 1.5 and 1.7 µm using both a supercontinuum source and superluminescent light emitting diodes. A system based upon an optical enhancement cavity of relatively high finesse, consisting of mirrors of reflectivity ∼99.98%, and a Fourier transform spectrometer, is demonstrated. Spectra are recorded of isoprene, butadiene, acetone and methane, highlighting problems with spectral interference and unambiguous concentration determinations. Initial results are presented of acetone within a breath-like matrix indicating ppm precision at <∼10 ppm acetone levels. Instrument sensitivities are sufficiently enhanced to enable the detection of atmospheric levels of methane. Higher detection sensitivities are achieved using the supercontinuum source, with a minimum detectable absorption coefficient of ∼4 × 10−9 cm−1 reported within a 4 min acquisition time. Finally, two superluminescent light emitting diodes are coupled together to increase the wavelength coverage, and measurements are made simultaneously on acetylene, CO2, and butadiene. The absorption cross-sections for acetone and isoprene have been measured with an instrumental resolution of 4 cm−1 and are found to be 1.3 ± 0.1 × 10−21 cm2 at a wavelength of 1671.9 nm and 3.6 ± 0.2 × 10−21 cm2 at 1624.7 nm, respectively.

Ultrashort Optical Pulse Propagation in terms of Analytic Signal

Abstract: We demonstrate that ultrashort optical pulses propagating in a nonlinear dispersive medium are naturally described through incorporation of analytic signal for the electric field. To this end a second-order nonlinear wave equation is first simplified using a unidirectional approximation. Then the analytic signal is introduced, and all nonresonant nonlinear terms are eliminated. The derived propagation equation accounts for arbitrary dispersion, resonant four-wave mixing processes, weak absorption, and arbitrary pulse duration. The model applies to the complex electric field and is independent of the slowly varying envelope approximation. Still the derived propagation equation posses universal structure of the generalized nonlinear Schrodinger equation (NSE). In particular, it can be solved numerically with only small changes of the standard split-step solver or more complicated spectral algorithms for NSE. We present exemplary numerical solutions describing supercontinuum generation with an ultrashort optical pulse.

High flux coherent supercontinuum soft X-ray source driven by a single-stage 10 mJ, kHz, Ti:sapphire laser amplifier

Abstract: We demonstrate the highest flux tabletop coherent soft X-ray source to date, using high harmonics driven by a single-stage Ti:sapphire-pumped OPA at 1.3µm. The spectrum extends to 200eV, with a flux of >106 photons/pulse/1% bandwidth.

Cavity Enhanced Spectroscopy of High-Temperature H2O in the Near-Infrared Using a Supercontinuum Light Source

Abstract: In this paper we demonstrate how broadband cavity enhanced absorption spectroscopy (CEAS) with supercontinuum (SC) radiation in the near-infrared spectral range can be used as a sensitive, multiplexed, and simple tool to probe gas-phase species in high-temperature environments. Near-infrared SC radiation is generated by pumping a standard single-mode fiber with a picosecond fiber laser. Standard low reflectivity mirrors are used for the cavity and an optical spectrum analyzer is used for the detection of gas-phase species in combustion. The method is demonstrated by measuring flame generated H2O in the 1500 to 1550 nm region and room-temperature CO2 between 1520 nm and 1660 nm. The broadband nature of the technique permits hundreds of rotational features to be recorded, giving good potential to unravel complex, convoluted spectra. We discuss practical issues concerning the implementation of the technique and present a straightforward method for calibration of the CEAS system via a cavity ringdown measurement. Despite the large spectral variation of SC radiation from pulse to pulse, it is shown that SC sources can offer good stability for CEAS where a large number of SC pulses are typically averaged.