Cylindrical-lens-based wavefront-reversing shear interferometer for the spatial coherence measurement of UV radiations

Spatial coherence of low-cost 532nm green lasers

“…The wavefront is reversed in one of interferometer arms by the retro-reflection by the plane mirror located at the focal plane of a cylindrical lens. In this interferometer 6 , the wave front in one arm can also be radially folded at any angle by the rotation of the cylindrical lens, facilitating coherence measurement even for rotationally asymmetric partially coherent beams. The lens can be either spherical or cylindrical.…”

“…The laser beam (~1mm size) was expanded via a beam expander, BE by a factor of 10. Then it passed the reversal shear interferometer and went to a screen, S. This interferometer is a modified Michelson interferometer consisted of only four optical components, namely an optical wedge (OW), a cylindrical/spherical lens (L of focus length of ~20mm) and two high-reflection mirrors (M1-M2) 6,7 . The wavefront is reversed in one of interferometer arms by the retro-reflection by the plane mirror located at the focal plane of a cylindrical lens.…”

“…That led to a series of interferometric measurements to find the dependences of spatial coherence on some parameters of the lasers employed. Experiments were performed by reversal shear interferometers developed in our laboratories not long ago 6,7 . The laser source under test was of the LP532A-30 model (DPSSFD type) of the industrial laser alignment series by Sky-lasers Shenzhen Keyuan Co. Ltd. 8 .…”

Analysis on the saturation of refractive index modulation in fiber Bragg gratings (FBGs) written by partially coherent UV beams

“…The UV (λ 255 nm) laser sources, UV 1 and UV 2 of different spatial coherence, were generated from β-BBO crystal (Type-I, cut angle 50°for λ 510 nm) based second harmonic frequency conversion of partially coherent CVL (λ 510 nm) oscillator beams with positive branch unstable resonator (PBUR) of magnification 12.5 and a generalized diffraction filtered resonator (GDFR) respectively [19]. The spatial coherence of these UV beams was studied with a homemade reversal shear interferometer [20]. The contrast of phase mask fringes is an important parameter in determining FBG reflectivity.…”

“…The high repetition rate (5.6 kHz) and low fluence/pulse UV (λ 255 nm) laser sources of different spatial coherent were generated from β-BBO crystal based second harmonic frequency conversion of copper vapor laser (CVL) (λ 510 nm) oscillator beams in different resonator configurations [19]. The spatial coherence of the writing UV beams was studied by a cylindrical lens based reversal shear interferometer, as described in [20]. The divergence CVL-UV follows that of fundamental CVL, which changes within a pulse [19].…”