Fig 7 - uploaded by Juerg Aus-der-Au
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(a) Laser cavity for elliptical-mode lasers. The Brewster-angled slab is pumped through a mirror coating on the left side. R indicates a cylindrical mirror for focusing in y direction. (b) Schematic for the laser cavity in (a), for the x direction only. f indicates the thermal lens, and f and f represent the focal lengths of mirrors R and R .
Source publication
We discuss in detail the effects of thermal lensing and thermally induced stress in end-pumped lasers with a strongly elliptical pump and laser mode and compare this situation with cylindrical rod geometries.
Contexts in source publication
Context 1
... a strategy to find a zone-I design meeting all mentioned requirements. The implementa- tion of this strategy led to a self-made computer program, which is based on a combination of analytical results with a numer- ical optimization algorithm. In the following, we describe the basic ideas. The type of laser cavity we considered is shown in Fig. 7(a). The gain medium has a highly reflective coating for the laser wavelength on one side, through which the pump power is applied. For two reasons, the laser cavity must be folded at this point. First of all, it can be shown that a standing-wave cavity with the thermal lens at one end always has to operate in zone II, because zone I ...
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... on the other end (which makes focussing on the absorber more convenient). A disadvantage of this cavity type is that the beam makes four instead of two passes through the gain medium per round-trip, doubling the effective strength of the thermal lens (but also the gain). The small mode size in direction is generated by a cylindrical mirror [ in Fig. 7(a)]. The structure of the cavity in direction, for which we can ignore the cylindrical mirror, is as shown in Fig. 7(b); it contains two curved mirrors , represented by lenses with the focal length and , and two flat end mirrors, apart from the thermal lens . Considering first only the direction, we can more or less freely choose four arm ...
Context 3
... the beam makes four instead of two passes through the gain medium per round-trip, doubling the effective strength of the thermal lens (but also the gain). The small mode size in direction is generated by a cylindrical mirror [ in Fig. 7(a)]. The structure of the cavity in direction, for which we can ignore the cylindrical mirror, is as shown in Fig. 7(b); it contains two curved mirrors , represented by lenses with the focal length and , and two flat end mirrors, apart from the thermal lens . Considering first only the direction, we can more or less freely choose four arm lengths for a given set of mirrors and . For an arbitrarily chosen set of the four arm lengths , one can now use the ...
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... S IGNIFICANT heat generation in the channel of GaNbased high-electron-mobility transistors (HEMTs) is one of the main causes of their performance degradation. Accurate characterization and modeling of transistor thermal impedance is, therefore, of paramount importance to most circuit designs [1], [2], [3]. ...
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... However, power saturation was also observed for higher pump powers because of an inevitable thermal lens effect. More measures such as compensation of the thermal lens effect, bonding undoped endcaps to the ceramic, 26) or employment of slab laser, 27) etc., should be taken into consideration in future efforts to obtain further output power enhancement. ...
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... High-power solid-state lasers rods are usually made from single-crystal Nd:YAG material [2][3][4][5]. Koechner [6] has pointed out that the r f of YAG is between 176-206 MPa, which corresponds to fracture longitudinal heat power densityP hf between 160 and 187 W cm -1 , in accordance with [7] ...
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... High average power solid-state lasers suffer from the limitation of the possible heat that could be dissipated from the active element (AE). Slab shapes give an advantage of increasing the surface at which heat can flow out of the AE which increase the amount of dissipated heat that could be extracted from the AE thus increasing the possible output power by increasing the pumping power [1][2][3]. The maximum incident pumping power is limited by the stress fracture, which is caused by non-uniform temperature distributions in the crystals with pump loading [4], also reducing temperature distribution resulting from increasing the dissipated heat permits a significant enhancement in beam performance. ...
... High average power solid-state lasers suffer from the limitation of the possible heat that could be dissipated from the active element (AE). Slab shapes give an advantage of increasing the surface at which heat can flow out of the AE which increase the amount of dissipated heat that could be extracted from the AE thus increasing the possible output power by increasing the pumping power [1][2][3]. The maximum incident pumping power is limited by the stress fracture, which is caused by non-uniform temperature distributions in the crystals with pump loading [4], also reducing temperature distribution resulting from increasing the dissipated heat permits a significant enhancement in beam performance. ...
An analytical solution of transient 3-D heat equation based on integral transform
method is derived. The result are compared with numerical solution, and good
agreements are obtained. Minimization of response time and temperature distribution
through a laser slab are tested. It is found that the increasing in the lateral
convection heat transfer coefficient can significantly reduce the response time and
the temperature distribution while no effect on response time is observed when
changing pumping profile from Gaussian to top hat beam in spite of the latter reduce
the temperature distribution, also it is found that dividing the pumping power
between two slab ends might reduce the temperature distribution and it has no
effect on thermal response time.
... High average power solid state lasers suffer from the limitation of the possible heat that could be dissipated from the active element (AE). Slab shapes give an advantage of increasing the surface at which heat can flow out of the AE which increase the amount of dissipated heat that could be extracted from the AE thus increasing the possible output power by increasing the pumping power [1][2][3]. The maximum incident pumping power is limited by the stress fracture, which is caused by non-uniform temperature distributions in the crystals with pump loading [4], also reducing temperature distribution resulting from increasing the dissipated heat permits a significant enhancement in beam performance. ...
... This effect, changes the optical path length, thus altering the properties of the selected mode at the output of the laser. The heating of the gain medium such as Nd:YAG crystal causes thermal lensing, and often the crystal start behaving like a lens [11]. Several methods have been used previously to measure thermal lensing in solid-state laser medium [3,4,12,13], in particular thermal lensing behaviour in Nd:YAG [5][6][7]14,15] . ...
In this paper we experimentally demonstrate the measurement of thermally induced lensing, using a Shack-Hartmann wavefront sensor. We measured the thermally induced lens from the coefficient of defocus aberration using a Shack-Hartmann wavefront sensor (SHWFS). As a calibration technique, we infer the focal length of standard lenses probed by a collimated Gaussian beam of wavelength 633 nm. The technique was applied to an Nd:YAG crystal that is actively pumped by a diode laser operating at 808 nm. The results were compared to the results obtained by changing the properties of the end-pumped solid-state laser resonator operating at 1064 nm, where the length of an unstable plane-parallel laser resonator cavity is varied, and the laser output power was measured.
... High average power solid state lasers suffer from the limitation of the possible heat that could be dissipated from the active element (AE). Slab shapes give an advantage of increasing the surface at which heat can flow out of the AE which increase the amount of dissipated heat that could be extracted from the AE thus increasing the possible output power by increasing the pumping power [1][2][3]. The maximum incident pumping power is limited by the stress fracture, which is caused by non-uniform temperature distributions in the crystals with pump loading [4], also reducing temperature distribution resulting from increasing the dissipated heat permits a significant enhancement in beam performance. ...
An analytical solution of transient 3D heat equation based on integral transform method is derived. The result are compared with numerical solution, and good agreements are obtained. Minimization of response time and temperature distribution through a laser slab are tested. It is found that the increasing in the lateral convection heat transfer coefficient can significantly reduce the response time and the temperature distribution while no effect on response time is observed when changing pumping profile from Gaussian to top hat beam in spite of the latter reduce the temperature distribution, also it is found that dividing the pumping power between two slab ends might reduce the temperature distribution and it has no effect on thermal response time.
... However, all of the pumped power from diode laser is not available for the laser active medium. Particularly in high power lasers, the heating of the gain medium often causes significant thermal effects that have been investigated in the literature [1,[5][6][7][8][9][10][11][12]. Thermal effects on laser rod bring lensing properties over the laser beam through the following mechanisms. ...
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