We report on the demonstration of broadband squeezed laser beams that show a frequency-dependent orientation of the squeezing ellipse. Carrier frequency as well as quadrature angle were stably locked ...to a reference laser beam at 1064 nm. This frequency-dependent squeezing was characterized in terms of noise power spectra and contour plots of Wigner functions. The latter were measured by quantum state tomography. Our tomograph allowed a stable lock to a local oscillator beam for arbitrary quadrature angles with {+-}1 deg. precision. Frequency-dependent orientations of the squeezing ellipse are necessary for squeezed states of light to provide a broadband sensitivity improvement in third-generation gravitational-wave interferometers. We consider the application of our system to long-baseline interferometers such as a future squeezed-light upgraded GEO 600 detector.
Status of the GEO 600 squeezed-light laser Khalaidovski, Alexander; Vahlbruch, Henning; Lastzka, Nico ...
Journal of physics. Conference series,
01/2012, Letnik:
363, Številka:
1
Journal Article
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In the course of the high-frequency upgrade of GEO 600, its optical configuration was extended by a squeezed-light laser 1, Recently, a non-classically enhanced measurement sensitivity of GEO 600 was ...reported 2, In this paper, a characterization of the squeezed-light laser is presented. Thereupon, the status of the integration into GEO 600 is reviewed, focussing on the sources of optical loss limiting the shot noise reduction by squeezing at the moment. Finally, the possibilities for a future loss reduction are discussed.
For coating Brownian thermal noise reduction in future gravitational wave detectors, it is proposed to use light in the helical Laguerre-Gaussian LG33 mode instead of the currently used LG00 mode. ...However, the simultaneous reduction of quantum noise would then require the efficient generation of squeezed vacuum states in the LG33 mode. Current squeezed light generation techniques employ continuous-wave second harmonic generation (SHG). Here, we simulate the SHG for both modes numerically to derive first insights into the transferability of standard squeezed light generation techniques to the LG33 mode. In the first part of this paper, we therefore theoretically discuss SHG in the case of a single undepleted pump mode, which, in general, excites a superposition of harmonic modes. Based on the differential equation for the harmonic field, we derive individual phase matching conditions and hence conversion efficiencies for the excited harmonic modes. In the second part, we analyse the numerical simulations of the LG00 and LG33 SHG in a single-pass, double-pass and cavity-enhanced configuration under the influence of the focusing, the different pump intensity distributions and the individual phase matching conditions. Our results predict that the LG33 mode requires about 14 times the pump power of the LG00 mode to achieve the same SHG conversion efficiency in an ideal, realistic cavity design and mainly generates the harmonic LG66 mode.
Thermal noise of the dielectric mirror coatings can limit laser-optical
high-precision measurements. Coatings made of amorphous silicon and silicon
nitride could provide a remedy for both ...gravitational-wave detectors and
optical clocks. However, the absorption spectra of these materials require
laser wavelengths around 2 $\mu$m. For GW detectors, ultra-stable laser light
of tens or hundreds of watts is needed. Here, we report the production of
nearly 30 W of ultra-stable laser light at 2128 nm by frequency conversion of
1064 nm light from a master oscillator power amplifier system. We achieve an
external conversion efficiency of (67.5 $\pm$ 0.5) % via optical parametric
oscillation and a relative power noise in the range of
$10^{-6}$/$\sqrt{\text{Hz}}$ at 100 Hz, which is almost as low as that of the
input light and underlines the potential of our approach.
Squeezed light is injected into the dark port of gravitational wave interferometers, in order to reduce the quantum noise. A fraction of the interferometer output light can reach the OPO due to ...sub-optimal isolation of the squeezing injection path. This backscattered light interacts with squeezed light generation process, introducing additional measurement noise. We present a theoretical description of the noise coupling mechanism. We propose a control scheme to achieve a de-amplification of the backscattered light inside the OPO with a consequent reduction of the noise caused by it. The scheme was implemented at the GEO 600 detector and has proven to be crucial in maintaining a good level of quantum noise reduction of the interferometer for high parametric gain of the OPO. In particular, the mitigation of the backscattered light noise helped in reaching 6dB of quantum noise reduction Phys. Rev. Lett. 126, 041102 (2021). The impact of backscattered-light-induced noise on the squeezing performance is phenomenologically equivalent to increased phase noise of the squeezing angle control. The results discussed in this paper provide a way for a more accurate estimation of the residual phase noise of the squeezed light field.
Continuous-wave (cw) squeezed states of light have applications in sensing, metrology and secure communication. In recent decades their efficient generation has been based on parametric ...down-conversion, which requires pumping by externally generated pump light of twice the optical frequency. Currently, there is immense effort in miniaturizing squeezed-light sources for chip-integration. Designs that require just a single input wavelength are favored since they offer an easier realization. Here we report the first observation of cw squeezed states generated by self-phase modulation caused by subsequent up and down conversions. The wavelengths of input light and of balanced homodyne detection are identical, and 1550 nm in our case. At sideband frequencies around 1.075 GHz, a nonclassical noise reduction of (2.4 +/- 0.1) dB is observed. The setup uses a second-order nonlinear crystal, but no externally generated light of twice the frequency. Our experiment is not miniaturized, but might open a route towards simplified chip-integrated realizations.
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