Flat-Top Converter

Converts Gaussian beam to a flat-top beam

Suitable for high LIDT applications and high-power lasers (63.4 J/cm² @ 1064 nm, 10 ns and 2.2 J/cm² @ 1030 nm, 212 fs)

High > 93% transmission @ 1030 nm (with AR coatings transmission > 99%)

Flat optics – saves space, easy to handle

Reliable and resistant surface – the structure is inside the bulk

Large structured aperture possible – up to 15 mm (standard substrate size Ø 25.4 x 3 mm)

Wavelength from 300 to 2000 nm

Conversion efficiency up to 70 % (wavelength dependent)

Space-variant waveplate for flat-top conversion is a space-variant phase retardation plate inscribed inside a bulk of fused silica glass by femtosecond laser pulses. It is well known that flat top intensity distributions compared to Gaussian beam profiles with respect to the efficiency and quality have noticeable advantages for micromachining. ⁴

A combination of a space-variant waveplate and a polarizer acts as a space-variant transmission filter (patent pending) and can be used to transform an initially Gaussian beam to a flat-top beam with efficiency of more than 50% of initial laser power.

Converter allows for on-the-fly adjustment of the beam shape from flat-top to shape with a dip in the middle. The converter is compatible with high power ultrashort lasers.

1. Gertus, A. Michailovas, K. Michailovas, V. Petrauskienė, “Laser beam shape converter using spatially variable waveplate made by nanogratings inscription in fused silica”, SPIE 9343, Laser Resonators, Microresonators, and Beam Control XVII, 93431S (March 3, 2015). doi:10.1117/12.2075869 
2. Michailovas, J. Adamonis, A. Aleknavicius, S. Balickas, T. Gertus, A. Zaukevičius, K. Michailovas, and V. Petrauskiene, “A New Beam Shaping Technique Implemented In 150 W 1kHz Repetition Rate Picosecond Pulse Amplifier”, OSA Technical Digest (online) (Optical Society of America), paper JTu5A.40A, (2016). doi:10.1364/CLEO_AT.2016.JTu5A.40
3. Adamonis, A. Aleknavičius, K. Michailovas, S. Balickas, V. Petrauskienė, T. Gertus, and A. Michailovas, “Implementation of a SVWP-based laser beam shaping technique for generation of 100-mJ-level picosecond pulses”, Applied Optics, Vol. 55, Issue 28, pp. 8007-8015, (2016). doi:10.1364/AO.55.008007
4. Homburg, O., & Mitra, T. (2012). Gaussian-to-top-hat beam shaping: an overview of parameters, methods, and applications. Laser Resonators, Microresonators, and Beam Control XIV. doi:10.1117/12.907914