A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

This Review discusses the emerging field of mid-infrared frequency comb generation, including technologies based on novel laser gain media, nonlinear frequency conversion and microresonators, as well as the applications of these combs in precision spectroscopy and direct frequency comb spectroscopy. Laser frequency combs are coherent light sources that emit a broad spectrum of discrete, evenly spaced narrow lines whose absolute frequency can be measured to within the accuracy of an atomic clock. Their development in the near-infrared and visible domains has revolutionized frequency metrology while also providing numerous unexpected opportunities in other fields such as astronomy and attosecond science. Researchers are now exploring how to extend frequency comb techniques to the mid-infrared spectral region. Versatile mid-infrared frequency comb generators based on novel laser gain media, nonlinear frequency conversion or microresonators promise to significantly expand the applications of frequency combs. In particular, novel approaches to molecular spectroscopy in the 'fingerprint region', with dramatically improved precision, sensitivity, recording time and/or spectral bandwidth may lead to new discoveries in the various fields relevant to molecular science.

Mid-infrared frequency combs

Ultrafast fibre lasers are an important optical system with industrial, medical and purely scientific applications. Essential components and the operation regimes of ultrafast fibre laser systems are reviewed, as are their use in various applications.

Ultrafast fibre lasers

We demonstrate a compact 20 Hz repetition-rate mid-IR OPCPA system operating at a central wavelength of 3900 nm with the tail-to-tail spectrum extending over 600 nm and delivering 8 mJ pulses that are compressed to 83 fs (<7 optical cycles). Because of the long optical period (∼13 fs) and a high peak power, the system opens a range of unprecedented opportunities for tabletop ultrafast science and is particularly attractive as a driver for a highly efficient generation of ultrafast coherent x-ray continua for biomolecular and element specific imaging.

90 GW peak power few-cycle mid-infrared pulses from an optical parametric amplifier

The generation of extremely short isolated attosecond pulses requires both a broad spectral bandwidth and control of the spectral phase. Rapid progress has been made in both aspects, leading to the generation of light pulses as short as 67 as in 2012, and broadband attosecond continua covering a wide range of extreme ultraviolet and soft X-ray wavelengths. Such pulses have been successfully applied in photoelectron and photoion spectroscopy and recently developed attosecond transient absorption spectroscopy to study electron dynamics in matter. In this Review, we discuss significant recent advances in the generation, characterization and applications of ultrabroadband, isolated attosecond pulses with spectral bandwidths comparable to the central frequency. These pulses can in principle be compressed to a single optical cycle. This review discusses significant recent advances in the generation, characterization and application of ultrabroadband isolated attosecond pulses with a spectral bandwidth comparable to the central frequency, which can in principle be compressed to a single optical cycle.

The generation, characterization and applications of broadband isolated attosecond pulses

We present a novel mid-IR source based on optical parametric chirped pulse amplification (OPCPA) generating 96 fs pulses (9.0 cycles) at 3.2 μm with an energy of 1.2 μJ, at a repetition rate of 100 kHz. The amplified spectrum supports a minimum Fourier transform limited pulse duration of 45 fs, or 4.2 cycles. Our use of OPCPA allows the direct amplification of few-cycle pulses at this mid-IR wavelength, and is inherently scalable to higher energies. The seed source for the system is based on difference frequency generation (DFG) between two outputs of the same fibre laser: this source is expected to be intrinsically CEP stable.

https://www.icfo.eu/images/publications/J09-025.pdf

Mid-IR short-pulse OPCPA with micro-Joule energy at 100kHz

An all-optical and passively carrier-to-envelope-phase-stabilized (CEP-stabilized) optical parametric chirped pulse amplification (OPCPA) system is demonstrated with sub-250-mrad CEP stability over 11 min and better than 100 mrad over 11 s. This is achieved without any electronic CEP stabilization loop for 160 kHz pulse repetition rate in the few cycle regime.

Sub-250-mrad, passively carrier-envelope-phase-stable mid-infrared OPCPA source at high repetition rate.

We present a novel mid-infrared (mid-IR) source of ultrashort pulses applicable to a wide range of biological, spectroscopic, and strong-field physics investigations. The source produces 67 fs pulses at 3.2 microns, with energy of 3.8 μJ at 100 kHz repetition rate and a pulse-to-pulse RMS stability of 0.7%. The system is based on OPCPA, is scalable in energy and repetition rate, and provides a platform for a new generation of ultrashort mid-IR sources.

New Mid-Infrared Light Sources

We report on the shortest pulses to date from a mid-IR optical parametric chirped pulse amplification: 67fs duration with 3.8μJ energy operating at 3.2μm. The system is all solid state and diode pumped and operates at 100kHz with unprecedented power stability of 0.75%rms over 30min.

Six-cycle mid-infrared source with 3.8 μJ at 100 kHz

We generate self-carrier-to-envelope phase-stable, 630 μJ pulses, centered at 2.1 μm, with 42 fs (6 cycle) duration based on collinear optical parametric amplification in BiB3O6 at 3 kHz. These pulses are generated through a traveling wave amplifier scheme, and the bandwidth supports 28 fs (4 cycle) pulse duration. Carrier-to-envelope phase stability was measured to be 410 mrad over 10 min or 260 mrad over 35 s.

Philip K. Bates

Papers

Mid-IR short-pulse OPCPA with micro-Joule energy at 100kHz

Sub-250-mrad, passively carrier-envelope-phase-stable mid-infrared OPCPA source at high repetition rate.

New Mid-Infrared Light Sources

Six-cycle mid-infrared source with 3.8 μJ at 100 kHz

High-average-power, carrier-envelope phase-stable, few-cycle pulses at 2.1 μm from a collinear BiB3O6 optical parametric amplifier.