Accurate iodine spectroscopy measurement plays important role in wavelength metrology, precise spectrum detection and interferometry measurement. In all the spectrum of iodine, the saturation absorption lines at 633 nm are the most widely used with the iodine stabilized He-Ne laser. Due to its weak output power, it is difficult to directly measure the absolute frequency with femtosecond frequency comb. In this paper, we present a new optical beating note system based on polarization maintaining fibers, which is employed to measure the weak iodine stabilized laser successfully. The experimental results show that a standard deviation of the frequency fluctuation of 12 kHz and a relative stability of 1.4×10-11 at 1 s are obtained, respectively. The reproducibility of the iodine stabilized laser is also studied, and a confident result of 3.8 kHz in peak to peak value is obtained with six months.
UV laser wavelength standard plays important role in UV wavelength meter and spectrograph calibrating, and it is also widely used in laser induced fluorescence, molecules phosphorescence, and alkali metals gas mixtures. Usually, the continuous wave UV laser sources are obtained by two-step second harmonic generation (SHG) effects from YAG:Nd lasers, or one-step SHG with the tunable dye lasers or diode lasers as fundamental beams. However, these laser systems are expensive and complicated. In this paper, we report a low costs and simple experimental arrangement to emit a fixed wavelength UV laser by a He-Ne laser. It takes the 632.8 nm He-Ne laser as the fundamental beam to generate the second harmonic in the nonlinear optical crystal of Beta barium borate (BBO), and obtains a 316.4 nm UV laser radiation with a power of 50 μW. Benefiting from the wavelength uncertainty of the He-Ne laser, the UV laser takes the same wavelength uncertainty of 5×10-6. It means that no extra stabilization techniques are needed for the some special applications with the lower wavelength accuracy requirement. The UV laser takes an intracavity SHG configuration with two concave reflectors of short focal length to form a folded cavity. The internal power of the fundamental beam is more than 100 mW when the BBO crystal is installed. The length of the bore tube is about 30 cm, and the cavity length is no more than 50 cm. To our knowledge this is the shortest cavity in the He-Ne laser intracavity SHG ever demonstrated.
Diode Laser wavelength standards at the 1.5 μm optical telecommunication band have important application in the dense wavelength division multiplexing (DWDM). This need motivates the frequency stabilization by Doppler-free spectra of the molecule overtone, such as acetylene 13C2H2 or 12C2H2, HCN and ammoni 14NH3. Especially, the P(16) line of 13C2H2 in the (ν1+ν3) band was adopted by the International Committee for Weights and Measures (CIPM) for practical realization of the definition of metre, which was given a uncertainty of 10 kHz with a relative uncertainty of 5×10-11. The recommended stabilized laser has elicited widespread interest in the national metrology institutes (NMIs). In this paper, we demonstrate an initially experimental result of the acetylene 13C2H2 stabilized laser using the Doppler-free spectra with one-way pump and probe configuration in the external acetylene cell. This stabilized near infrared laser employs a commercial external cavity tunable diode laser with the classic Littman-Metcalf configuration, and it could be applied in the optical fiber communication as a wavelength reference standard. A home-made 3f detection and servo system is taken to lock the external cavity tunable diode laser (ECDL) at the Doppler-free transition of the 13C2H2 P(16) line with one-way pump and probe configuration. The initial experiment results show that a standard deviation of the frequency fluctuation of 2.7 kHz and a relative stability of 4.2×10-13 at 100 s are obtained, respectively. In the future, we will focus on the optimization of these systems, including disciplining the acousto-optic shift frequency to an atom clock and optimizing the parameters of the closed loop.
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