High power single frequency for Interferometry

02 Aug 2018

The resolution of an interferometer is dependent on the linewidth of the illuminating laser, wavelength stability and its absolute wavelength. UniKLasers introduce a range of single frequency lasers designed for the highest resolution interferometry in a wide range of wavelengths.

Interferometry is a method of measuring small surface changes by monitoring the diffraction pattern of two interfering laser beams, one reference and one that is incident on the object. Sharp interference bands produced by a narrow line width laser improve accuracy of measurement and the shorter wavelengths can differentiate between smaller surface changes. Additionally, any movement in the wavelength of the laser will blur the interference, so laser stability must not be taken for granted.

UniKLasers Ltd, Edinburgh, UK, designs and manufactures single frequency lasers in a wide range of wavelengths using a technique called Bragg Range Michelson Mode Selection (BRaMMS). The technique replaces an end cavity mirror with a volume Bragg grating and Michelson interferometer to create the mode selectivity of a single mode laser. The result is an ultra-stable laser output that is mode-hop and drift free and has a high spectral purity with linewidths below 500 kHz (coherence lengths well over 100m). Since the VBG reflectivity is limited to a small wavelength range, it can be selected to promote a range anywhere in the output bandwidth of the gain media. This increases the wavelength options available, which means fundamental wavelengths can be used rather than frequency doubled options, the increased efficiency leads to higher available power and reduced thermal management requirements.

With the wavelength now being a function of cavity length, the stability of the output is reliant on reducing fluctuations in the position of the end mirrors. This is easily compensated for by using PZT control linked to a feedback mechanism that corrects any expansion/contraction of the laser head. This feedback loop has the added benefit in that it allows for a fine tunability of the wavelength output, or alternatively locking the absolute frequency to an external reference.

The lasers are therefore ideal for such applications as

• Holography
• Interferometry
• Brillouin Scattering
• Raman Spectroscopy
• Quantum technology

To find out more about the UniKLasers product range, the BRaMMS technique or to get further information please visit our web site, contact us directly or, if you are visiting the SPIE Optics and Photonics show, discuss it in person, we will be on booth #633 with our USA distributor RPMC Lasers.