The recent advances in laser optics are reviewed. Some problems, which are of interest for further study of the optical beam characterization, propagation and transformation are proposed and briefly analyzed.

The history, present situation and future of optical frequency standards and optical frequency measurements were presented. The uncertainty of optical frequency standards has come up to 10-11 ~ 10-14. In this way, length unit 'meter' became the derived unit of time unit 'second'. Recently, there was a great breakthrough in this field. The unexpected link of femtosecond mode-locked laser and optical frequency measurement technology make a simple relation between microwave standards and optical frequency standards. Frequency measurements get easier and more accurate because of this relation. This is a new brilliancy in metrology and physics.

We studied that the transfer matrix ABCD theorem for the passage of paraxial rays or the optical system possessing a rotational symmetry axis can be generalized for the skew rays propagated off-axis, whether the optical system possessing rotational symmetry axis or not. We noticed that the same ABCD relation exists in the classical mechanics also. This fact hints samething more need to be considered. As a consequence, the connection of ABCD theorem with the fundamental " uncertainty principle " in quantum mechanics had been established. Furthermore we applied the general ABCD theorem to evaluate the diffraction integral, matrix elements A ~ D expressed in terms of the angular eikonal function T, and the primary aberration included. Finally the numerical results in the case of only spherical aberrations are presented.

A completely new type of solid-state round travelling-wave laser was presented. The resonator consists of only two concave mirrors and one of them is coated on the curved surface of the laser material. Between the mirrors the laser beam travelled in a closed 3-dimensional loop. Oscillations of many kinds of round travelling-wave laser modes have been observed , and lasers pumped at two defferent points on the active material have been developed. The experimental results indicates that the novel laser has most simple structure and very stable output. Using this design, high-efficient laser, single-frequency laser and mode-locked laser with short cavity length can be developed.

The research progress on image reconstruction technique from few projections for limited view optical tomography was described. It includes orthographic double object beam system for holographic interfreometry, modified simultaneous algebraic reconstruction technique (MSART), frequency spectrum approach reconstruction technique (FSART), and neural network reconstruction technique (NNRT).

Quasi-phase-matching is a technique for phase matching nonlinear optical interactions which the nonlinear coefficient is modulated spatially at regular intervals using a structural periodically built into the nonlinear medium. Using this technique, higher conversion efficiency can be obtained and nonlinear interactions over the entire transmission band of the material can be utilized. In particular, the periodically poled domain structure in LiNbO3 has become the most important sample, which was fabricated by domain engineering. The development and trend of quasi-phase-matching technique are introduced in detail.

Perovskite oxide thin films and heterojunctions have been fabricated by laser molecular beam epitaxy controlled in atomic scale. Measurements of atomic force microscopy (AFM) and high-resolution transmission electron microscopy (HRTEM) reveal that the surfaces and interfaces of the thin films and heterojunctions are atom-level-smooth. The optically transparent oxide thin films with transmittances higher than 85% in the visible region have been fabricated. The electrical and optical properties of BaTiO3-x thin films and BaTiO3/SrTiO3 (BTO/STO) superlattices were examined. The BaTiO3-x thin films have the properties of insulator, semiconductor or conductor with different oxygen content. The coefficient of the second harmonic generation of BTO/STO is 23 times larger than that of bulk BaTiO3 crystal. We observed the current and voltage modulations of La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3 p-n junctions by applied magnetic fields and found that the p-n junctions exhibited the positive colossal magnetoresistance (CMR) behavior for the first time.The CMR ratio (△R/R0,△R=RH-R0) are 46.7% and 83.4% in 5 Oe,and 1000 Oe at 255 K for LSMO/SNTO p-n junction;and the positive CMR ratio as large as 515% at 100 K at 3T in LSMO/SNTO multilayer p-n heterostructure are found.

Fabrication of three-dimensional microstructures and microdevices based on femtosecond laser modification and machining of transparent materials has attracted much attention. Microfabrication techniques and their applications are introduced, including femtosecond laser induced refractive index change for fabrication of optical waveguides, gratings and couplers;microexplosion inside materials for three-dimensional bit-oriented storage and other dot-arrayed structures;interface ablation for drilling, cutting and etching;two-photon polymerization for microlens, photonic cryatals and diffractive optical elements.

The properties of femtosecond laser and the mechanisms of femtosecond laser micromaching are introduced, the differences to that of long-pulse laser are emphasized. Femtosecond laser produce high intensity and offer precision breakdown threshold with lower laser fluence. The femtosecond laser micromachining has a very limited heat-affected volume. These advantages of femtosecond laser could be applied in precision micromachining of various materials. Femtosecond laser micromaching can have a micron and submicron feature size. Some femtosecond laser micromachining results, including comparison with long-pulse, are discussed, and the widespread application prospect is described.

Recent developrments of the spectroscopic and chemical techniques used most frequently for the measurements of atmospheric trace gases were reviewed, with the emphasis on the differential optical absorption spectroscopy (DOAS), the differential absorption Li-dar (DIAL), the Fourier transform spectrometer(FTS) and the tunable-diode laser absorption spectroscopy (TDLAS). The chemical techniques involved the gas chromatograph, mass spectrometer and their combination, the chemoluminescent methods, the matrix isolation and electron spin resonance as well as gas supersonic expansion and laser induced fluorescence, etc.. The wide range spectroscopic measurements, the combination of spectroscopic and chemical technologies as well as the trends of instrument miniaturization were disscussed as the potential technologies in the future.

The characteristics of laser sources and mechanisms of interaction between laser and tissue were introduced. The new development of application of laser in medicine was summarize, specially, in vein, oncology, vision, dermatology and Chinese medicine. A reference for the new clinical application of laser in medicine is provided.

Previous works on the theoretical models of pulsed laser ablation were summarized. Our recent studies of the physicochemical processes and mechanisms for pulsed laser ablation of metal oxides were briefly reviewed. A novel thermal-controlling mechanism was proposed for the pulsed laser ablation of metal oxides when the laser fluence was not very high.

The advances in micromaser studies were reviewed, with the emphases on the micromaser injected with ultra-cold atoms. The fundamental theoretical methods and the main results were presented, and the experimental situation was also briefly introduced.

Recent investigations on quantum interference effects were introduced, including line-shape variation, spontaneous emission enhancement or cancellation, constructive interference and electromagnetically induced transparency in molecular and atomic-molecular mixed systems in our laboratory. It is instructive to the researches about quantum interference and control in molecular, condensed matter and material systems.

In the realm of quantum information, cavity QED is the most effective scheme that can realize the quantum information process. In cavity QED, the core is the interaction between atoms and cavity modes. Based on the frequencies of atomic transitions and cavity modes, we can divide the interaction into two different kinds, one is the resonant interaction where the atomic transition frequency is equal to cavity mode frequency, the other is the large-detuned interaction where the atomic transition frequency is large detuned from the cavity mode frequency. From the two different kinds of interaction we all can prepare entangled states, teleport unknown states and realize the quantum logic gates. By comparison, we conclude that the large-detuned interaction scheme would become a promising scheme, and would make the realization of quantum network and quantum computer possible in the near future.

Recent progress in polymer optical fiber (POF) and functional devices is summarized, especially, the researches in our lab. At the same time, the applications of POF devices and products in the communication and photoelectron are discussed.

When the core index is increased by using doped GeO2 technology in photonic crystal fiber (PCF), light is more easily confined by not only the air holes, but also the raised-index core. By numerical solving Helmholtz equation with finite differential (FD) method, some performances were studied about PCF that transverse cross sections consist of a central high-index defect in a regular triangular array of air holes. The dispersion difference is visible under all kind of doped proportion in core when the core and air hole sizes are fixed. Higher doped proportion in core will bring higher effective index of PCF and make the dispersion parameter decreasing. Furthermore, increasing the air hole sizes with fixed core size and index will make the dispersion become higher, effective index decreasing and effective area of modal field decreasing. Especially, the changing trend is little different under all kinds of doped proportion in core.

Metal-semiconductor-metal (MSM) structure photodetectors have many advantages, including easy fabrication, simple wafer structure with only one mono-dopant active layer, and excellent potential to achieve high quantum efficiency and high speed. In this paper, we demonstrated fabrication of 4H-SiC UV photodetector with MSM structure by using nickel as Schottky contact. The result shows that detector has very low dark current;at the bias about 15 V, the density of dark current is about 70 nA/cm2. The illuminated current of the detector is about two orders magnitude higher than the dark current. The ratio of the responsivity about 290 nm to that at 380 nm is greater than 1000, implying that those devices have a great improved visible blind performance.