Experiments to Control Atom Number and Phase-Space Density in ...
Experiments to Control Atom Number and Phase-Space Density in ...
Experiments to Control Atom Number and Phase-Space Density in ...
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7.3 Optical Setup<br />
Multiple laser systems, operat<strong>in</strong>g at different frequencies, <strong>and</strong> imag<strong>in</strong>g setups are<br />
required <strong>to</strong> trap, cool, manipulate <strong>and</strong> image the a<strong>to</strong>mic ensemble. A near-resonant laser<br />
system is used <strong>in</strong> the Zeeman slower, the MOT setup, <strong>and</strong> for imag<strong>in</strong>g. A far-detuned<br />
CO2 laser provides the optical potential for evaporative cool<strong>in</strong>g, <strong>and</strong> an Nd:YAG laser<br />
will be used <strong>to</strong> create the tweezer trap for laser cull<strong>in</strong>g.<br />
7.3.1 Near-Resonant Laser System<br />
Two low-power diode lasers (Toptica, DLpro), each with an output power of ap-<br />
proximately 20 mW, <strong>and</strong> one tapered amplifier with its own master laser diode (Toptica,<br />
TApro) with an output power of approximately 400 mW constitute the near resonant<br />
laser system. A schematic of the near-resonant laser table is shown <strong>in</strong> figure 7.26.<br />
7.3.1.1 Spectroscopy Setup<br />
A phase modulation spectroscopy setup is used <strong>in</strong> the lithium experiment. The<br />
optical layout is shown <strong>in</strong> figure 7.27. A pair of anamorphic prism pairs (Thorlabs,<br />
PS871-B) shapes the elliptical beam of the laser diode <strong>to</strong> a more circular beam shape.<br />
After the prism pair, the beam passes through an optical isola<strong>to</strong>r (Conoptics, model<br />
712B). This optical isola<strong>to</strong>r protects the diode from potentially harmful back-reflections.<br />
Us<strong>in</strong>g a half-wave plate (CVI-MellesGriot, QWPM-670-05-2) <strong>and</strong> a polariz<strong>in</strong>g beam<br />
splitter cube (CVI-MellesGriot, PBS-670-050) the beam is distributed <strong>in</strong><strong>to</strong> two beam<br />
paths. About 5 mW of power are transmitted through the cube for the spectroscopy<br />
setup, the rest of the power (about 15 mW) is diverted <strong>to</strong> the frequency offset lock (see<br />
chapter 7.3.1.3).<br />
The current of the laser diode is modulated at 20 MHz by the PDD module of the<br />
laser electronics (Toptica). This causes sideb<strong>and</strong>s at ±20 MHz of the carrier frequency.<br />
The beam (with all three frequency components) double passes the spectroscopy cell<br />
<strong>and</strong> the signal is detected <strong>in</strong> a fast pho<strong>to</strong>diode (New Focus, model 1801). The voltage<br />
signal is transmitted <strong>to</strong> the PDD module, which generates the error signal. Figure 7.28<br />
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