Wang Su-Mei

A random number generator based on quantum entangled photon pairs

A new scheme for a random number generator based on quantum entangled photon pairs is demonstrated. Signal photons produced by optical parametric down-conversion are detected at two single-photon detectors after transmission or reflection at a 50/50% beamsplitter, to form a truly random binary sequence. Their arrival is signalled by their twin idler photons, so that a cw laser source may be used instead of attenuated laser pulses. Coincidence measurement is employed to obtain the bit sequences, which are shown to fully satisfy the standard tests for randomness.

Diode-Pumped Self-Q-Switched Cr,Nd:YAG Laser with High Average Output Power

A diode end-pumped self-Q-switched Cr,Nd:YAG laser was established with pulse duration in the range of 8–10 ns. The maximum average output power was 4.4 W and the slope efficiency was 27% using an output coupler of R = 70%. At pumping power of 17.4 W the laser produces high-quality pulses at 1064 nm in a TEM00-mode.

Wideband Antireflection Film Fabricated by Glancing Angle Deposition

Graded-index ZrO2 films has been fabricated on K9 glass by glancing angle deposition. Because the index mismatch at the interface has been reduced, the film results in wideband high-transmission antireflection. From 400nm to 1200nm, the film reflection is lower than 0.8% and the lowest value is 0.2% at 432nm.

Form Birefringence in Thin Films with Oblique Columnar Structures

Effective medium theory is useful for designing optical elements with form birefringent subwavelength structures. Thin films fabricated by oblique deposition are similar to the two-dimensional surface relief subwavelength gratings. We use the effective medium theory to calculate the anisotropic optical properties of the thin films with oblique columnar structures. The effective refractive indices and the directions are calculated from effective medium theory. It is shown that optical thin films with predetermined refractive indices and birefringence may be engineered.

Green Output of 1.5 W from a Diode-Pumped Intracavity Frequency-Doubled Self-Q-Switched and Mode-Locked Cr,Nd:YAG Laser

The spontaneous emmission (SE) progress of polarized atoms in a stratified structure of air-dielectric (D0-metal(M)-dielectric(D1)-air can be controlled effectively by changing the thickness of the D1 layer and rotating the polarized direction of atoms. It is found that the normalized SE rate of atoms located inside the D0 layer crucially depends on the atomic position and the thickness of the D1 layer. When the atom is located near the D0-M interface, the normalized atomic SE rate as a function of the atomic position is abruptly onset for the thin D1 layer. However, with the increasing thickness of the D1 layer, the corresponding curve profile exhibits plateau and stays nearly unchanged. The substantial change of the SE rate stems from the excitation of the surface plasmon polaritons in metal-dielectric, and the feature crucially depends on the thickness of D1 layer. If atoms are positioned near the D0-air interface, the substatial variation of the normalized SE rate appears when rotating the polarized direction of atoms. These findings manifest that the atomic SE processes can be flexibly controlled by altering the thickness of the dielectric layer D1 or rotating the orientation of the polarization of atoms.

Diode-pumped passive Q-switched 946 nm Nd : YAG laser with a GaAs saturable absorber

We report, for the first time to our knowledge, a diode-pumped passive Q-switched 946 nm Nd:YAG laser by using a GaAs as saturable absorber. The maximum average output power is 1.24 W at an incident pump power of 15 W, corresponding to a slope efficiency of 10%. Laser pulses with pulse duration of 70 ns and repetition rate of 330 kHz are generated.

Spectroscopic investigation of a new crystal: Nd3+,Yb3+:YVO4

The absorption and emission spectra of the YVO4 single crystal co-doped with 1 at.% Nd3+ and 1 at.% Yb3+ are investigated. The efficient Nd3+ → Yb3+ energy transfer and the back transfer (Yb3+ → Nd3+) are observed at room temperature. The fluorescence lifetime of the 4F3/2 level of Nd3+ in Nd, Yb:YVO4 is measured under 808 nm laser light excitation. The efficiency of Nd3+ → Yb3+ energy transfer in YVO4 is determined to be about 34%.

Diode end-pumped self-Q-switched and mode-locked Nd,Cr:YAG /KTP green laser

We first experimentally demonstrate a laser-diode end-pumped self-Q-switched and mode-locked Nd,Cr:YAG green laser with a KTP crystal as the intra-cavity frequency doubler. The device produces an average output power of 680 mW at 532 nm. The corresponding pulse width of the Q-switched envelope of the green laser is 170 ± 20 ns. The mode-locked pulses have a repetition rate of approximately 183 MHz and the average pulse duration is estimated to be around sub-nanosecond. It is found that the intra-cavity frequency doubling greatly improves the modulation depth and stability of the mode-locked pulses within the Q-switched envelope.