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A laser system for the parametric amplification of electromagnetic fields in a microwave cavity
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View: Figures


Image of FIG. 1.
FIG. 1.

Conceptual setup of the laser system.

Image of FIG. 2.
FIG. 2.

Scheme of the Nd:YAG rod amplifier and wavelength conversion sections of the laser. After amplification at constant section in the rods, the beam is reduced in size by the telescope T3 (magnification M = 0.5) to increase the conversion efficiency in a LBO crystal (dimensions: 4 × 4 × 15 mm3). An harmonic separator (SA) reflects the 532 nm light to pump an OPO cavity. The mirror M19 transmits the idler beam and reflects the signal wavelength to the cryostat outside the clean room. Photodiodes PD1 and PD2 monitor the macropulse shape, respectively, before and after second harmonic generation.

Image of FIG. 3.
FIG. 3.

(Dots) Autocorrelation measurement of the laser pulse width after the OPO stage. The continuous line is the best fit obtained with a squared hyperbolic secant function, corresponding to a pulse width of 7.2 ps.

Image of FIG. 4.
FIG. 4.

Scheme of the electronic feedback used to stabilize the master oscillator repetition frequency. A fast photodiode monitors the oscillator output, which is compared to a reference microwave generator inside the frequency synthesizer ADF4108. Its output controls the high voltage fed to a piezoelectric transducer (PZT) which adjusts the length of the cavity.

Image of FIG. 5.
FIG. 5.

Tuning of the repetition rate around the central frequency. The maximum change that can be obtained is 1.6 MHz.

Image of FIG. 6.
FIG. 6.

A 15-h measurement of the master oscillator frequency stability obtained with an Agilent spectrum analyzer ESA E 4405-B.

Image of FIG. 7.
FIG. 7.

Plot of the AOM driver function, for two different values of current delivered to the diodes in the pre-amplifier stage. The function is stepwise with a 10 ns discretization time. The lower curve, corresponding to 103 A, allows to extract a greater macropulse energy.

Image of FIG. 8.
FIG. 8.

Oscilloscope trace of the train of laser pulses emerging from the OPO cavity at about 800 nm, taken with a 50 ps rise time photodiode (Hamamatsu C4258) placed after the engineered diffuser (see Sec. IV). The horizontal scale is 50 ns/division. The limited sampling of the oscilloscope does not allow to reproduce accurately each single 12 ps pulse.

Image of FIG. 9.
FIG. 9.

Laser beam profile: (left) before entering the Nd:YAG rods; (right) after passing through the two rods; diffraction patters are kept within acceptable limits.

Image of FIG. 10.
FIG. 10.

Optical parametric oscillator output for two different pump energies: (left) 20 mJ macro-pulse total energy; (right) 40 mJ macro-pulse total energy.

Image of FIG. 11.
FIG. 11.

Optical scheme to uniformly illuminate the semiconductor. The laser beam is focused onto the surface of the GaAs disk through an engineered diffuser. The square inset shows the power density at the semiconductor surface, recorded with a CCD camera set at the position of the GaAs disk. The circle defines the area to be illuminated.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: A laser system for the parametric amplification of electromagnetic fields in a microwave cavity