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Thermo-optical phase modulator for femtosecond pulse management

English title Thermo-optical phase modulator for femtosecond pulse management
Applicant Lüthy Willy
Number 117609
Funding scheme Project funding (Div. I-III)
Research institution Institut für angewandte Physik Universität Bern
Institution of higher education University of Berne - BE
Main discipline Technical Physics
Start/End 01.01.2008 - 31.12.2009
Approved amount 124'386.00
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Keywords (8)

thermo-optical phase modulation; femtosecond pulse compression; two dimensional phase modification; adressable focus position; Two-dimensional phase modulator; Thermo-optical phase modulator; femtosecond pulse shaping; overcompensating dispersion

Lay Summary (English)

Lead
Lay summary
In the Framework of SNSF project 200020-109262/1 “High-resolution adaptive mirror” a thermally activated phase modulator was developed that can easily be steered with a digital video projector in connection with a personal computer. With this system an experiment was performed to re-compress the dispersion-broadened pulse of a femtosecond laser. This experiment was extremely successful. A 52 femtosecond pulse was dispersion broadened with a BK7 glass block to a duration of several hundred femtoseconds. With the aid of the phase modulator it could be re-compressed, better than the original laser pulse. Since the 4f zero dispersion stretcher produces a line focus, in this experiment only one-dimensional pulse shaping was used. In view of the extremely good result, the further potentials of this device will be explored. This investigation will involve three main activities:
(i) Technical improvement of the modulator cell and the required software to optimize the pulse shape;
(ii) Two-dimensional pulse shaping will be performed by splitting the line focus of the 4f zero dispersion stretcher. With the improved modulator precisely defined multiple pulses or single pulses with predetermined shape will be generated.
(iii) By overcompensating the dispersion broadening, the compressed pulse can appear at a given position inside a dielectric medium. At the position of the optimum pulse compression it will induce nonlinear processes that can be used for materials processing or diagnostics. Since in this case focussing with a lens is not necessary to reach high intensity, this process can also be applied at a given position in the core of a fibre.
The proposed work is not only performed for a specific application. It is much more an exploration of the potential of a thermo-optically driven phase modulator in the field of femtosecond pulse shaping.
Femtosecond pulse shaping is generally performed with phase modulators based on liquid-crystal matrices. Thermo-optically driven modulators, however, are non-pixelated devices that do not give rise to diffraction at pixel boundaries. It can therefore be expected that better results can be achieved than with liquid crystal matrices.
Further it may be pointed out that the thermo-optically driven phase modulators are rather simple and robust and that the costs of such a system are mainly given by the price of the digital light projector. That is much more than one order lower in price than comparable systems.
Direct link to Lay Summary Last update: 21.02.2013

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Associated projects

Number Title Start Funding scheme
126553 Two-dimensional phase shaping for electron acceleration 01.01.2010 Project funding (Div. I-III)
109262 High-resolution adaptive mirror 01.10.2005 Project funding (Div. I-III)
126553 Two-dimensional phase shaping for electron acceleration 01.01.2010 Project funding (Div. I-III)

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