Advanced applications of wavelength tunable lasers in metrology and fundamental physics

In this thesis, measurement systems based on wavelength tunable lasers have been developed and studied to improve measurement capabilities in the fields of optical metrology and quantum optics. In the first work presented in this thesis, techniques for precision measurements of absolute spectral irradiance responsivity of detectors were investigated. Two laser-based methods and a traditional monochromator based method were compared in the near infrared wavelength region. The results between absolute responsivity measurements using the three different measurement systems demonstrated agreement at the uncertainty level of less than 0.1 % (k = 1). The second work consists of an acetylene-stabilized laser and an optical single-frequency synthesizer that were constructed and characterized for precision optical frequency measurements at telecommunication wavelengths. The acetylene-stabilized laser was designed by taking a fiber-based approach, which enabled a relatively straightforward implementation of the optical set-up. The frequency of the stabilized-laser was measured absolutely using an optical frequency comb generator. The results agree well with the recommendation by the International Committee for Weights and Measures (CIPM). The single-frequency synthesizer was designed for generating a single user-specified frequency from an atomic time base within the 192–196 THz gain bandwidth of an erbium-doped fiber amplifier (EDFA). The synthesizer was utilized for studying spectral lineshapes of acetylene transitions near 1540 nm. The recorded spectra were investigated by theoretical fits and the obtained line-center frequencies were compared to line-center frequencies measured with the acetylene-stabilized laser using the third harmonic technique. The results agreed well with each other. Final part of the thesis describes a set-up that is capable of emitting indistinguishable single photons using single molecules as photon sources. This was achieved by combining high resolution laser spectroscopy and optical microscopy at cryogenic conditions. Two single molecules in separate microscopes were identified and DC-Stark effect was exploited to shift the resonance frequencies of given molecules for perfect spectral overlap. Excitation by pulsed laser enabled triggered generation of identical single photons from two independent single molecules. The results can be utilized in the development of a number of different quantum information processing schemes.