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A quick guide on how to choose laser crystal cut
When choosing laser crystals one has to decide which crystal cut to use, i.e. how the end faces of the crystal will be cut. Generally, there two different cuts are used in laser crystals: right-angle cut and Brewster-angle cut.
Fig. 1. Right-angle cut (a.) and Brewster-angle cut (b.) of Ti:Sapphire laser crystal. L stands for crystal length.
Figure 1 shows the visual difference between the two cuts in Titanium doped sapphire crystals: right-angle cut has the polished ends perpendicular to the axis of propagation of light; whereas Brewster-angle cut crystals are at Brewster’s angle between the normal vector of the polished face and axis of light input. In the figure this angle is 60.4°. For laser beam propagation from air to laser crystal (with refractive index n), Brewster’s angle is defined as θB=arctan(n). At Brewster’s angle, the surface reflectance is zero for the light with polarization inside the plane defined by the direction of light propagation and the normal to the surface (also defined as p-polarized light).
Right-angle cut is easier to manufacture than Brewster-angle cut, however it leads to higher resonator losses. It is convenient for application of anti-reflective, high reflection or partial reflecting coatings, but is not very useful in high power, especially short-pulse, applications. Coatings applied to the crystal usually have lower damage threshold than uncoated Brewster-angle cut crystal faces.
Brewster-angle cut is used to eliminate reflection losses, increase polarization contrast, avoid formation of parasitic pulses in ultra-short pulse oscillators or even induce negative dispersion. Brewster cut faces are left uncoated in order to increase damage threshold of the surface. Reflection loss of p-polarization is Brewster-angle cut crystals is zero.
Brewster-angle cut crystals are more expensive than right-angle cut crystals because the former require more raw material to get the same crystal length L.
Table below summarizes the differences between the two cuts
|Right-angle cut||Brewster-angle cut|
|Laser induced damage threshold||Lower, if dielectric coatings are applied||Higher|
|Reflection losses||Higher, if no AR coatings are applied||Zero reflection losses for p-polarized light|
|Other||Additional recurring repolishing/
recoating costs due to damaged
coatings over time
|Astigmatism induced under high average
As a rule of thumb, right-angle cut crystals are often chosen when the applications require cost effective solution and when the aim of application isn’t to get the maximum output of lasing power, whereas Brewster-angle cut crystals are chosen when the application is to get maximum power output keeping in mind that the polarization of pumping laser has to be parallel to the plane of incidence of the laser crystal for best results.
Altechna - 18 years in photonics
Altechna is a supplier of laser related products and solutions, specializing in the following key activity fields:
- Laser related components.
- Distribution of well-known photonics industry brands in local markets.
- R&D solutions in laser micromachining.
- Manufacturing of laser related components.
- Quality assurance and measurements to guarantee the highest quality.
Our products and solutions are based on added value for the customer:
- Highly qualified sales staff dedicated to specific geographic regions.
- Aim to build long lasting relationship with our customers.
- Each product is shipped only after passing meticulous quality control department.
- Growing number of standard products available from stock.
- Experience in providing customized products for customers in various fields. o Focused growth of company group allows to provide diverse added value solutions.
We hope that you may be interested in our products, solutions, services and possibility to work with us.
Clean and protect optics with special polymer film
Product is safe to use with nanostructures, precision surfaces, optics, glass, fused silica, silicon, crystals, non-linear crystals, metals, Ge, ZnSe, NaCl, KBr, KRS-5, first surface mirrors, telescope optics and precision aerospace surfaces. First Contact™ also cleans and protects diffraction gratings, phase masks, and pinholes.
You may order the product or pre-coating service for any Altechna optics. Our metrology laboratory engineers will apply protective film after optics quality inspection.
Order stock laser optics and get protection film for free. For more information on this offer please visit www.instockoptics.com
Coating technologies at Altechna
Our coatings cover wavelength range from deep UV (193 nm) to far IR (25 µm) with biggest part of coatings done in wavelength ranges of most conventionally accessible laser and illumination sources from 266 nm to 2 µm.
We offer a set of standard and custom coatings per individual request:
- Anti-reflection coatings
- High reflection coatings
- Beam splitter coatings
- Partially reflective coatings
- Polarizer coatings
- Filter coatings
- Ultrafast GDD compensated coatings
- Gires-Tournois interferometer mirrors (GTI)
- Variable reflectivity mirrors
- Metallic coatings
Each coating is special and over the years in the photonics field we have learned that flexibility is the key to meet high demands of our customers therefore our coatings are done using different technologies which are chosen for separate coatings individually. Here is our list of coating technologies available at Altechna:
- Electron beam evaporation
- Ion assisted deposition
- Ion beam sputtering
Each technology is different and is used according to requirements of spectral sensitivity, damage threshold, hardness, surface quality etc.
Best optical quality inspection practise at Altechna
Visual inspection begins with optical surface quality inspection and visual examination according to Military 13830 and ISO 10110 standards.
Altechna also executes effective focal length measurement from 5 mm to 5000 mm and radius of curvature measurement from 7 mm to 700 mm. Lens centration measurement unit is available with 'Multilens' software for multi lens system measurement and analysis.
We perform transmittance from 190-1100 nm and reflectance measurement at 0° and 45° angles.
The laboratory carries out wavefront distortion measurements diffraction and aberration analysis surface figure of flat and spherical surfaces per 100 mm diameter.
Moreover we offer: angle measurements of various elements with 0,4 arcsec accuracy; waveplates retardation measurement using Soleil-Babinet Compensator, Axicons Bessel beam generation measurement.
Each product is followed with detailed quality report. For more information please visit www.altechna.com.
Tradeshows and events
Official event website: www.optatec-messe.com
PHOTONICS. WORLD OF LASERS AND OPTICS'2014
We would like to invite you to meet us at stand no. 71C13.
Fore more details please visit official exhibition website.
LASER OPTICS BERLIN 2014
Altechna will be participating in Laser Optics Berlin exhibition in Berlin, Germany on 18-20 of March.
We would like to invite you to meet us at stand 12/205.
Fore more details please visit official exhibition website.
SPIE Photonics West 2014
To arrange scheduled meeting please contact [email protected]
Laser World of Photonics
Visit us in hall B1, booth no.553.