Common use of Experiment Clause in Contracts

Experiment. Our folded optical resonator (Fig. 5.1) consists of three highly reflective mirrors (nominal specification R > 99.995%). The folding angle is 90◦, the radii of curvature of mirror M1 and MF are 1 m, mirror M2 is planar, and all mirrors have a diameter of 2.5 cm. Fig. 5.2 shows the complete experimental setup. The length of arm A2 is 1.2 cm, the length of arm A1 is variable. We probe the transmission of the resonator with a beam at a wavelength of 532 nm, produced ∼ by a frequency-doubled single-mode Nd:YAG laser. The beam is sent to the resonator via lens L1, enters the cavity through mirror M1 (here the beam diameter is 0.5 mm) and excites the Hermite-Gaussian modes of the cavity. The focal length of lens L1 equals distance A3, so that the (dotted) beam is injected parallel to the optical axis, independent of the rotation- angle of mirror M3. This allows us to vary Δr, the off-axis position of injection on mirror M1, ∼ ∼ independent of the angle of injection. We inject in the xz-principal plane or in the y-principal plane in order to excite only 1-dimensional TEMm0 or TEM0m modes. Exciting a limited set of modes makes labelling of the modes easier and allows us to measure closer to degeneracy. The spectrum is obtained from the spatially integrated throughput as a function of the cavity length, by scanning the position of mirror M1 with a piezo-element. Judging from these spectra, we estimate the finesse of the cavity as 5600 for low-order modes and 5000 for high-order modes. This is considerably smaller than the value of the finesse allowed by the mirror reflectivities (> 99.995%). We attribute this discrepancy mainly to scattering due to polishing errors of the mirrors.

Experiment. Our folded optical resonator (Fig. 5.1) consists of three highly reflective mirrors (nominal specification R > 99.995%). The folding angle is 90◦, the radii of curvature of mirror M1 and MF are 1 m, mirror M2 is planar, and all mirrors have a diameter of 2.5 cm. Fig. 5.2 shows the complete experimental setup. The length of arm A2 is 1.2 cm, the length of arm A1 is variable. We probe the transmission of the resonator with a beam at a wavelength of 532 nm, produced ∼ by a frequency-doubled single-mode Nd:YAG laser. The beam is sent to the resonator via lens L1, enters the cavity through mirror M1 (here the beam diameter is 0.5 mm) and excites the Hermite-Gaussian modes of the cavity. The focal length of lens L1 equals distance A3, so that the (dotted) beam is injected parallel to the optical axis, independent of the rotation- angle of mirror M3. This allows us to vary Δr, the off-axis position of injection on mirror M1, ∼ ∼ independent of the angle of injection. We inject in the xz-principal plane or in the y-principal ∼ ∼ plane in order to excite only 1-dimensional TEMm0 or TEM0m modes. Exciting a limited set of modes makes labelling of the modes easier and allows us to measure closer to degeneracy. The spectrum is obtained from the spatially integrated throughput as a function of the cavity length, by scanning the position of mirror M1 with a piezo-element. Judging from these spectra, we estimate the finesse of the cavity as 5600 for low-order modes and 5000 for high-order modes. This is considerably smaller than the value of the finesse allowed by the mirror reflectivities (> 99.995%). We attribute this discrepancy mainly to scattering due to polishing errors of the mirrors.