An optical-tweezers-based dual-frequency-band particle tracking system was designed and fabricated for liquid vis cosity detection. On the basis of the liquid viscosity dependent model of the particle’s restricted Brownian motion with the Fax´en correction taken into account, the liquid viscosity and optical trap stiffness were determined by fitting the theoretical prediction with the measured power spectral densities of the particle’s displacement and velocity that were derived from the dual-frequency-band particle tracking data. When the SiO2 beads were employed as probe particles in the measurements of different kinds of liquids, the measurement results exhibit a good agreement with the reported results, as well as a detection uncertainty better than 4.6%. This kind of noninvasive economical technique can be applied in diverse environments for both in situ and ex situ viscosity detection of liquids

  Energy transfer upconversion (ETU) coefficient plays a crucial role in investigating complex laser systems as it greatly influences both the laser output behavior and heat generation. For some quasi-three-energy-level lasers based on Er3+ doped, Ho3+ doped and codoped gain media, the available theoretical studies relied on some unreasonable approximations due to the lack of spectroscopic data, notably the ETU coefficient. We put forward what we believe is a novel approach to overcome the difficulties caused by wavelength jump occurred in aforementioned laser systems. Based on net gain cross-section analysis and rate equations modelling, the functional relationship between the ETU coefficient, the laser power and pump power at the jumping wavelength are established. ETU coefficients and their temperature dependences of Er,Yb:YAB crystals with different crystal doped concentrations are experimentally determined for the first time. The results reveal that the ETU process in Er,Yb:YAB laser system is 5∼35 times stronger than that in Er3+ and Yb3+ codoped phosphate glass. The determination of these spectroscopic data paves the way for precise modelling of laser system based on Er,Yb:YAB or similar gain media.

  A wavelength tuning method suitable to watt-level continuous-wave single frequency solid-state laser (CWSFL) at 1.5 µm was proposed. Based on a dual-gain-medium resonator design, the laser wavelength can be tuned by manipulating the combined net gain spectrum. Comparing with the traditional tuning method, the wavelength tuning range was eight times broader and extended to 0.438 nm, the maximum laser power was raised up to 0.64 W, which was the highest record for the 1.5 µm CWSFL to the best of our knowledge. The laser intensity noise reached the shot noise limit at the analysis frequency above 3.5 MHz. Wider wavelength tuning band of 5.58 nm can be expected when the same resonator design including two gain media with different doped concentrations was used, according to our theory.

  A real time deterministic quantum teleportation over a single fiber channel was implemented experimentally by exploiting the generated EPR entanglement at 1550 nm. A 1342 nm laser beam was used to transfer the classical information in real time and also acted as a synchronous beam to realize the synchronization of the quantum and classical information. The dependence of the fidelity on the transmission distance of the fiber channel was studied experimentally with optimizing the transmission efficiency of the lossy channel that was established to manipulate the beam of the EPR entanglement in Alice’s site. The maximum transmission distance of the deterministic quantum teleportation was 10km with the fidelity of 0.51±0.01, which is higher than the classical teleportation limit of 1/2. The work provides a feasible scheme to establish metropolitan quantum networks over fiber channels based on deterministic quantum teleportation.