G&H Presents Seven Papers at Photonics West 2015

Scientists from Gooch & Housego are proud to present seven papers at Photonics West 2015, highlighting the breadth of technological expertise the organization offers.

SPIE 9347-9: Fiber-Integrated Second Harmonic Generation Modules for Visible and Near-Visible Picosecond Pulse Generation
Thomas Legg, Tuesday 10 February, 11.00

We report on the development of fiber coupled frequency doubling modules and their application to novel picosecond pulse sources in the visible and near-visible. The modules are compact and robust, utilising a simple single-pass configuration with periodically-poled lithium niobate (PPLN) as the nonlinear conversion medium. Two sources integrated with the modules operating at 780nm and 560nm are presented. Picosecond pulsed laser sources in the visible and near-visible spectral region are interesting for biophotonic imaging applications involving super resolution microscopy, such as stimulated emission depletion microscopy (STED).

SPIE 9346-21: LN Q-switch for high gain lasers over an extended temperature range
Dieter Jundt, Wednesday 11 February, 08.45

Because of their modest cost as compared to other solutions, lithium niobate Q-switches are typically used in portable Nd:YAG lasers. To avoid undesirable pre-lasing due to insufficient Q-switch hold-off, the pyro-electric charges created on temperature change need to be neutralized. We have recently developed chemically reduced Q-switches that solve this problem by dissipating the charges through a layer of increased conductivity below the optical faces. We present results on different configurations of reduction treatment and compare the effect of large temperature changes on these crystals as well as untreated samples. The reduction treatment increases the optical loss but this is tolerable in high gain lasers and the effect also diminishes at longer wavelengths.

SPIE-9354-26: Compact dual channel optical fiber amplifier for space communication applications
Gary Stevens, Monday 9 February, 16.00

We are presenting results of radiation testing of our rad-hard Erbium-doped Fiber Amplifiers (EDFAs) for satellite communication applications. Optical Laser communication has been identified as the technology to enable high-data rate links between and within satellites, as well as between satellites and ground stations. EDFAs are a key part of this technology and G&H have been developing space-qualified modules. Our EDFA was subjected to radiation levels that would be found in Low-Earth Orbit (LEO) and Geo-synchronous orbit (GEO) and demonstrated that it would exceed the requirements necessary for in-orbit operation.

SPIE-9436-23: Optical isolators for 2-micron fiber lasers
Gary Stevens, Wednesday 9 February, 16.00

We are presenting results from our range of optical isolators for use in 2-micron fiber laser systems that have been developed recently as part of the FP7 project ISLA. Fiber lasers operating at 2-micron are becoming increasingly used in applications such as plastic welding, surgery and sensing. As part of our portfolio of 2-micron components, (which includes fused fiber and Acousto-optic devices) we have developed high performance optical isolators, which are essential for preventing back reflections from de-stabilising laser operation and damaging components.

SPIE 9359-13, Acousto-Optic Tunable Filter for imaging application with high performance in IR region
Stefano Valle, Mon 9 February 16.30

Acousto-Optic Tunable Filters with large acceptance angles are the component of choice for imaging applications in visible and NIR regions, but there is a practical limit on the RF power at wavelengths above 2µm. A proposed solution to reduce the RF power requirement is to configure an AOTF, to operate at acoustic resonance. A special RF driver is required in order to maintain in resonance the device. Experimental results of the first prototype of a resonant AOTF operating between 1-2µm have been compared to theoretical values with excellent agreement; an advantage of factor of four has been measured. Potential applications for the resonant AOTF include aerospace and space environments where control of RF power budget and temperatures management are crucial.

SPIE 9369-6: A high-performance passband-agile hyperspectral imager using a large aperture acousto-optic tunable filter
Christopher Pannell, Wednesday 11 February 10.30

We present innovations in acousto-optic tunable filters (AOTF) based hyper-spectral imaging. An AOTF offers wavelength scanning under 200 microseconds allowing an “image cube” to be built up with spectroscopic information about every pixel. Analysis of this data cube allows for example, the separation of a number of overlapping spectra. If each spectrum is the signature of a particular dye or compound, this allows us to determine the percentage of each type of dye, and therefore the material, in every pixel. One application of this is in cervical cancer detection using high-throughput screening, where a sample of tissue is stained with a cocktail of dyes, each one designed to register the presence of a particular type of protein.  The key proteins can be rapidly “assayed” using our scanner, which can change wavelengths up to 1000X faster than liquid crystal based competing technologies.

SPIE 9369-2 The spatially-heterodyned spectrometer: an ideal tool for Raman work?
Christopher Pannell, Wednesday 11 February 10.30

G&H are currently investigating high throughput spectrometers that capitalize on our expertise in glass engineering, precision polishing, and material adhesive-free bonding (Hy-Per BondTM). All these techniques are needed to realize a so-called Static Fourier Transform Spectrometer (SFTS), in which an interferometer together with a CCD detector form the instrument “core” in contrast to more conventional dispersive spectrometers. The big advantage of the SFTS is that it has up to several hundred times greater light throughput than a “classical” dispersive spectrometer, due to a monolithically-construed interferometer as opposed to a conventional slit+grating design. The particular form of SFTS we are concentrating on is the so-called Spatially Heterodyned Spectrometer (SHS), which allows great design flexibility, and is ideally suited to obtaining high spectral resolution over a relatively narrow range of wavelengths. Applications include Optical Coherence Tomography (OCT) and Raman Spectroscopy, where very low levels of scattered light are encountered.