Control of Thermal Lensing Effect in Transparent Liquids by Femtosecond Laser Pulses

Abstract

The thermal lensing effect in transparent (linear and nonlinear) molecular liquids can be modulated by disrupting continuously output 82 MHz 28 fs laser pulses at 800 nm to form trains of various widths ( t ) with respect to the thermal diffusivity time th ($ 2 ms). We present nonlinear refraction results for CHBr 3 (bromoform) obtained by the Z -scan technique. The results show that the thermal lensing effect increases with t when t is less than th , but becomes steady when t exceeds th and reaches 30 ms. The proposed technique of modulating the thermal lensing effect by varying t has great application potential in information photonics and optoelectronic devices, such as variable optical attenuators, holographic recording media, optical limiters and optical switches.

Thermal lensing effect of CS2 studied with femtosecond laser pulses

“…By integrating eqn (7), with eqn (6) substituted in, over the whole beam cross section we obtain the pulse energy of the ith pulse…”

“…[1][2][3][4][5][6][7] When the nanosecond (ns) order pulse-to-pulse separations t p-p 's (reciprocal of the repetition rates) are considerably shorter than the sub-millisecond (sub-ms) to ms order thermal diffusivity time constant t th , 8 the observed negative lensing effect, which strengthens with time relative to the leading pulse (denoted by T) within t th and gradually stabilizes as T exceeds t th , is ascribed to the thermal lensing effect. [1][2][3][4][5][6][7] When the nanosecond (ns) order pulse-to-pulse separations t p-p 's (reciprocal of the repetition rates) are considerably shorter than the sub-millisecond (sub-ms) to ms order thermal diffusivity time constant t th , 8 the observed negative lensing effect, which strengthens with time relative to the leading pulse (denoted by T) within t th and gradually stabilizes as T exceeds t th , is ascribed to the thermal lensing effect.…”

“…The thermal lensing effect induced in various simple liquids by femtosecond (fs) laser pulses delivered at repetition rates of tens of MHz has been studied with the Z-scan technique. [1][2][3][4][5][6][7] When the nanosecond (ns) order pulse-to-pulse separations t p-p 's (reciprocal of the repetition rates) are considerably shorter than the sub-millisecond (sub-ms) to ms order thermal diffusivity time constant t th , 8 the observed negative lensing effect, which strengthens with time relative to the leading pulse (denoted by T) within t th and gradually stabilizes as T exceeds t th , is ascribed to the thermal lensing effect. The multi-photon excitation processes have been commonly offered to explain this heat generation.…”

“…The multi-photon excitation processes have been commonly offered to explain this heat generation. [1][2][3][4][5][6][7]9 In this study we further explore the mechanism of the thermal lensing effect induced in CS 2 , an example of a simple liquid. In the experimental part of this work, we used a self-mode locked Ti:Al 2 O 3 laser which continuously delivers TEM 00 mode laser pulses at a repetition rate of 82 MHz.…”

Investigation of the optical absorption of a magnetic colloid from the thermal to the electronic time-scale regime: measurement of the free-carrier absorption cross-section

“…In the second case, the entire transmitted beam is detected by the photodetector and is named open-aperture configuration. The ZS technique has been extensively used to investigate nonlinear properties of different materials [3][4][5][12][13][14][15][16][17]. The Sheik-Bahae formalism (SBF) assumes a local interaction between the sample and the radiation field, disregarding thermal (nonlocal) phenomena, which are considered in the thermal-lens model (TLM) proposed in the 1960s [18][19][20].…”