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The pressure of radiation in a refractive medium has been a matter of theoretical controversy for many years, though relatively few experiments have been performed. We have measured the photon drag effect in germanium and silicon in the far-infrared, up to a wavelength of 1.2 mm. At sufficiently long wavelengths the effect is independent of the semiconductor band structure and depends on the radiation pressure in the dielectric. We find that the expression originally deduced by Minkowski correctly describes our results.

For the first time optically detected cyclotron resonance (ODCR) has been demonstrated using a CO, pumped far-infrared (FIR) laser instead of mircowaves. Both the electron and the light-hole cyclotron resonances have been observed in GaAs, as well as the 1 S to 2p + impurity transitions. Valence band quantum effects, well known in Ge, are resolved directly for the first time in GaAs and the electron cyclotron resonances show strong spin doublet in the highest quality MBE samples. The technique has remarkable resolution and sensitivity at low temperatures and, by constrast with other techniques that have been reported, we also observe the n = 1 to 2 (polaron shifted) and higher spin doublet split resonances at helium temperatures and with low FIR laser power. The conduction band results are analysed on the five-band model and the implications of this model on the valence band results are discussed. We have determined the valence band inverse mass parameters to be: ;' , = 7.5, 7, = 2.6, y3 = 3.1, K = 1.0.

Novel far-infrared optically detected cyclotron resonance (FIR-ODCR) techniques are used to investigate GaAs epilayers and t h e resuits are compared with conventional cyclotron resonance performed at far-infrared frequencies and ODCR at microwave frequencies. The FIROOCR technique shows remarkable resolution and sensitivity and has been applied to investigations of t h e electronic structure of low-dimensional systems. In particular. cyclotron resonance has been optically detected in a GaAsIGaAIAs multiple quantum well ( M a w ) sample and compared with ODCR results performed at microwave frequency. Multi-single quantum wells (MSOW) in an MBE GaAsIGaAIAs structure with different well thicknesses have also been investigated, and by detecting cyclotron resonance via the.FlR-induced changes in the luminescence of the separate wells, the power of the technique to investigate the cyclotron resonance mass versus well thickness in a single sample has been demonstrated. Finally. t h e experimentally determined values of effective mass for different well widths are compared with the theoretical results, showing good agreement.

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The capability level of rotary as well as first generation drilling operation could not be matched for deeply drilling programs. To reach that deep, the increasing in drill string length could also cause an additional constraint on hydraulic performance. The operation of slim hole drilling has significant potential to reduce well costs. This cost might be savings are especially important with increased demand for reduced capital finance under current economic conditions in the Iranian oil and gas industry. This savings achievement could be caused by use of smaller drilling rigs, work over rigs, reduced casing size, reducing requirement for drilling consumables and other costs associated with hole size. Otherwise, using laser irradiation for drilling operation can save cost little more higher look like do not using casing and perforation in reservoir layer for slim hole which are drilled by high power laser systems. As the matter of fact, Cost savings achieved from slim hole drilling could be offset by inability to effectively transmit the weight to the bit, increased mechanical failures of drill pipes and tools and reduced the well bore instability effects in particular, in drilling operation at greater depths This paper investigates the effects of borehole parameters during laser drilling operations in the case of slim hole.

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Laser rock spallation is a rock removal process that utilizes laser induced thermal stress to fracture and cause a break through the rock by creating small fragments before melting of the rock. In this paper we investigated the effects of CO 2 laser irradiation on limestone of Iran Sarvak formation. Since the limestone included heavy and light oil, we studied the amount of laser beam absorption by this oils for determining thermal fractured during the laser drilling laboratory process. In order to characterize this limestone spectrophotometry (from UV to NIR), scanning electron microscopy (SEM) have been used.