Application of optical parametric oscillators to photoacoustic studies in semiconductors

Observation of Phenomena After Pulsed Laser Irradiation of Solid with Optical Wave Microphone

“…It is known that pulsed laser irradiation of a solid results in a photothermal acoustic wave, which propagates within the solid and into the medium, when the laser energy is smaller than that for ablation. The photothermal acoustic wave induced inside the solid has been measured by piezoelectric transducers directly, 12) however, it is difficult to detect that emitted into the medium because the generation efficiency of the photothermal acoustic wave from a solid is as low as 10 À12 to 10 À8 . 13) When the laser energy is larger than the ablation threshold, a shock wave is induced by explosively ablated species, which can be observed with optical methods such as beam deflection, [14][15][16] Schlieren and Shadowgraph methods.…”

Photo-acoustic response and optical features of 2D-TlGaSe2 and GaAs semiconductors

“…For large energies above 1.425 eV the absorption depth becomes smaller than the area element which can propagate acoustically, therefore acoustic pressure starts to decrease following dependence ~1/α [10]. Previously, the PA pressure measurements in GaAs were performed after the similar nanosecond laser duration with a piezoelectric transducer attached to the back of the sample and were reported by Song et al [12]. Song's results check well with our PAS measurement in the energy range 1.4-1.75 eV as shown in Fig.…”

“…The GaAs was chosen because it is a well-established semiconductor in the photo-acoustic studies with femtosecond-to-nanosecond duration laser pulses on a wide spectral range [11,12]. The GaAs samples were obtained from a high quality two-inch double polished 0.5 mm thick (100) commercial wafer with an impurity content below 10 15 cm -3 .…”

“…1(c) [10]). Two mechanisms of PAS formation should be considered seriously in the case of a semiconductor: the thermoelastic process as a result of laser pulse absorption, and the deformation mechanism which is based on the change of electronic volume as a result of e-h pair generation [12,14]. One-dimensional equation for such lattice displacements can be solved analytically [14].…”

“…In usual detection schemes, a piezoelectric transducer is placed on the sample back side to detect the time-dependent strain of acoustic wave [12]. In our experiment, we used the Schlieren approach which as a method was first described for application in liquids and gases [10].…”