Fine tuning

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A laser-based gas analyser that employs novel optical parametric oscillator (OPO) technology was a finalist in this year’s SPIE Prism Awards.

Referred to as the ‘Oscars for optics’, the Prism Awards for Photonics Innovation is an international competition that honours the best new photonic products on the market. The prizes are presented annually at the Photonics West trade show in San Francisco.

The gas analysers from French firm Blue Industry and Science are the first to be based on a broadly tuneable laser, according to the firm. They are able to quantify traces of hundreds of molecules directly and operate in real time, making them ideal for applications such as industrial process monitoring.

The broadly tuneable laser combines high resolution (<0.01cm-1 typical) with a wide spectral tunability. These two characteristics are not easily compatible – the wider the tunability, the harder it is to keep a good spectral resolution.

The wide tunability is achieved by adding a small optical cavity to the laser, which is an evolution of OPO technology; it uses the properties of non-linear optics. From the source beam of the laser, the OPO cavity generates two output beams (called idler and signal).

By changing some parameters of the OPO cavity in real time, it is possible to tune the output beam over a very wide spectral bandwidth (2 x 800cm-1), while keeping the spectral characteristics
of the laser (the difficult part).

OPOs are usually limited to lab applications because they are – by nature – unstable optical cavities, according to the company. ‘A lot of our efforts were put in to develop (and patent) effective and robust controls to “tame the mustang” and make it a reproducible, repeatable device, that includes no moving parts,’ Blue Industry and Science said.

A set of software-controlled instructions triggers routines in the OPO to generate the idler beam at the desired wavelengths, anywhere in the spectral range of the idler.

Schematically, the total idler bandwidth is divided into hundreds of contiguous spectral zones of a few wavenumbers, and each of these zones works like a single laser, which can be activated on demand to measure the target molecules. There is no limit to the number of such ‘virtual lasers’ that can be activated.

Currently, Blue Industry and Science is finalising beta-tests at select partners and customers for its prism-award winning Blue X-FLR8 v2 model, but it is selling other gas analysers based on its broadly tuneable laser technology into indoor air quality, process analytics and health safety environment applications.

OPOs and OPAs: latest products

Coherent’s Fidelity 10 and Fidelity 18 ultrafast fibre lasers offer high stability, high average power, short pulse width and superior beam quality, making them well-suited to pumping tuneable optical parametric oscillators (OPOs) or non-linear fibres.

The Fidelity 10 and Fidelity 18 offer 10W and 18W of output power respectively, with a pulse width of 140fs and a wavelength of 1,040nm. Combining these parameters with the additional M2<1.2 beam quality of the lasers, a significantly high peak power and focused intensity is offered. Plus, the software-adjustable, internal pre-compensator allows users to optimise the pulse width and peak power of the laser at the sample or workpiece.

These features make the reliable Fidelity lasers suitable for many, high brightness, ultrafast applications. For example, in optogenetics, the high power will enable simultaneous photo activation of larger neural cell populations, supporting increasingly complex experiments. The lasers will also deliver faster imaging speeds in multiphoton excitation (MPE) applications. In addition, their stability, high power and superior beam quality make the lasers well-suited for microprocessing applications, such as scribing, two-photon rapid prototyping, waveguide writing, microfluidics, and surface processing.

Qioptiq, an Excelitas Technologies company, offers the IFlex-Agile, a high-power, continuous-wave (CW) OPO that features optimised optics for a full wavelength range to enable seamless operation. This instrument’s high-precision optics ensure excellent focusing and consistent beam emission for superior accuracy.

Ideal for mass spectrometry, material testing, spectroscopy and metrology applications, this compact instrument enables the fine-tuning of specific wavelengths from the NIR to MIR, for very narrow output beams of high intensity. Fully controlled through a USB computer interface, the IFlex-Agile enables rapid and reproducible settings of any desired wavelength from 1.47-2.0µm and 2.3-3.8µm, without the need to change optics or modules. The IFlex-Agile’s emission linewidths can vary from 500GHz to below 1MHz depending on the configuration and specific application.

The modular concept of the OPO enables modification of the wavelength tuning range, emission linewidths and output power levels in order to cost-efficiently meet custom requirements for specific applications, including trace-gas analysis, material inspection, chemical reactions and IR-detector calibration. The IFlex-Agile can also be customised upon request for extended wavelength range and narrow linewidth at 2,300-3,800nm.

The Taccor OPO-X from Laser Quantum is a GHz optical parametric oscillator (OPO) providing tuneable femtosecond pulses in the NIR wavelength regions with beam quality M2<1.2.

It is an ideal choice to add new wavelength ranges to GHz repetition rate ti:sapphire lasers, such as Laser Quantum’s Taccor Tune. The Taccor OPO-X is tuneable from 1,010-1,500nm in the NIR and from 505-740nm in the VIS, with an optional IR range also available. It also comprises an integrated high-resolution spectrometer.

Photonic Solutions offers a large range of collinear and non-collinear OPAs from Light Conversion, global specialists in OPA technology. The Orpheus family is a series of fs/ps OPAs for use with the Pharos and Carbide lasers (pumped at 1,030nm). The Orpheus OPAs maintain all the excellent features of Light Conversion's hugely successful Topas series of OPAs: high pulse stability throughout the tuning range, excellent beam quality, full computer control via USB, as well as options to extend the tuning range from the UV right up to the mid-IR.

Within the Orpheus family you will find a classic collinear OPA; the Orpheus-HP and Orpheus-HE (allowing pump powers/energies up to 40W and 2mJ); and the new Orpheus-F, an impressive hybrid OPA combining the short pulse durations of a non-collinear OPA, with the broad tuning range of a collinear one.