Studies on Spatial, Spectral, and Energy Characteristics of Copper-HBr Laser Radiations

Studies on high power second-harmonic deep-UV generation from a high repetition-rate Cu-HBr laser

“…It was observed that the far-field intensity distribution of the SHG-UV beam was centrally peaked (quasi-Gaussian) and corresponded to beam divergence of about 2× diffraction limit (DL) which almost followed the far-field beam divergence of the pump beam of about 1.9× DL (discussed in sub-section 4a). For quasi-Gaussian near-field spatial beam intensity profile of Cu-HBr laser radiation, the diffraction limited divergence is given as θ DL = 3.05 λ/D where λ is wavelength of radiation and D is the near-field laser beam diameter [7]. The long term stability of the SHG-UV power was measured to be about 7% (±3.5%), which is attributed to combined effects of the pump beam quality attributes and thermal induced processes as discussed in section 4.…”

“…For each resonator used, the experiment was carried out for different focal length values of f 3 (3 cm to 10 cm) and different pump beam average powers (P ω ⩽ 10 W, to prevent the crystal damage) varied using the beam splitter M 3 . The fundamental beam-quality attributes (divergence, pointing instability etc) were monitored by sampling out the beam using an optical wedge (W) in similar manner as described elsewhere [7].…”

“…It is clear from the above relations that both P 2ω and η 2ω are functions of f, θ and P ω even at ∆k = 0 (ideal/perfect conditions). Further both θ and P ω of a CVL are dependent on the operating temperature, PRR, active medium composition and resonator used with the CVL [7,19]. In view of this the beam quality attributes (beam divergence: θ, divergence fluctuation: ∆θ, intensity fluctuation: ∆I ω /I ω , pointing stability: δ, pulse duration: τ ω , average output power: P ω ) of the used Cu-HBr laser were studied for different resonators employed, in parallel, using a beam analysis software in a similar fashion as reported earlier [7] Further, for all the cases, the recorded spatial intensity profile was centrally peaked (quasi-Gaussian).…”

“…Further both θ and P ω of a CVL are dependent on the operating temperature, PRR, active medium composition and resonator used with the CVL [7,19]. In view of this the beam quality attributes (beam divergence: θ, divergence fluctuation: ∆θ, intensity fluctuation: ∆I ω /I ω , pointing stability: δ, pulse duration: τ ω , average output power: P ω ) of the used Cu-HBr laser were studied for different resonators employed, in parallel, using a beam analysis software in a similar fashion as reported earlier [7] Further, for all the cases, the recorded spatial intensity profile was centrally peaked (quasi-Gaussian). For a given resonator magnification M (hence, for given θ and P ω ), as f value decreased, the fast increase in P 2ω , η 2ω as well as the slopes of the graphs are attributed to the relations (4), ( 5) as well as relations ∂P 2ω /∂f ∝ 1/f 2 and ∂η 2ω /∂f ∝ 1/f 2 (figures 3(a) and (b).…”

“…These include efficient manufacturing of fibre gratings & other photonic components; UV-photolithography; micromachining of semiconductors/glass/ceramics/polymers; spectroscopy; and biology/genetics/medicine [1][2][3][4][5][6]. Among the limited choices available, the UV source (λ ≈ 255.3 nm) based on second harmonic generation (SHG) of copper vapour laser (CVL) radiation (λ ≈ 510.6 nm) is advantageous owing to its higher PRR and excellent spatio-temporal & spectral beam quality attributes as compared to that of excimer lasers and frequency quadrupled solid state lasers [3][4][5][6][7][8].…”