The development of laser technologies defined the novel quality demands to optical interference coatings. For many technological applications is very important to use lasers with equal distribution of laser intensity across the beam. Gradient mirrors is one of the most simple and convenient means to manage spatial distribution of laser radiation, and can be used in various lasers and laser devices. These mirrors are used as output coupler in the laser cavity to form radiation close to the Gaussian distribution which using radially varying thickness that have been proved the most practical. Multilayer dielectric mirrors with a smooth changing reflection are used in various types of laser resonators. However, in practice, not equal distributions take place especially for Q-switch lasers. It can be arise due to as mode structure of laser irradiation, as optical defects of rod. So, application of such mirrors, permit realize the selection of transverse modes in which the minimal losses possess the transverse mode with amplitude distribution close to distribution of mirror reflection. This paper presents the methodology of fabricating multilayer dielectric mirror with altering over surface parameters of reflectance.
A method for detecting ultralow quantities of explosives in air with use a state-of-the-art picosecond chip Nd3+:YAG laser has been developed. The method combines field asymmetric ion mobility spectrometry (FAIMS) with laser ionization of examined air samples. Radiation of λ = 266nm, τpulse = 300ps, Epulse = 30–150μJ, ν = 20–300Hz was used. Processes in the ion source for the use both picosecond and nanosecond ionization modes were analyzed. Parameters of the laser ion source have been specially optimized. The dependences on frequency, pulse energy, peak intensity, and average power for trinitrotoluene (TNT) and cyclotrimethylenetrinitramine (RDX) were obtained. It was shown that the optimal peak intensity should be no less 3·106 W/cm2. The detected ion signals for all explosives were shown to be threefold higher for picosecond excitation in comparison with use a nanosecond laser of the same average power. The estimated detection threshold of the prototype equals 1. 10-15 g/cm3. The results are promising for the development of a highly sensitive, portable laser explosive detector.
A method for detecting ultralow quantities of explosives in air and explosive traces using a state-of-the-art picosecond
chip Nd3+:YAG laser has been elaborated. The method combines field asymmetric ion mobility spectrometry (FAIMS)
with laser ionization of air samples and laser desorption of analyzed molecules from examined surfaces. Radiation of the
fourth harmonic (λ = 266 nm, τpulse = 300 ps, Epulse = 20-150 μJ, ν = 20-300 Hz) was used. The ionization efficiencies for
trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX), and glyceryl trinitrate (NG) were investigated. The
dependences on frequency, pulse energy, peak intensity, and average power for TNT and RDX were determined. It was
shown that the optimal peak intensity should be no less than 2∙106 W/cm2; at lower peak intensities, the increase of the
average laser power in the interval 5–15 mW enhanced the ion signal. The results of detection of TNT, RDX, and NG
vapors under these conditions were compared with the results obtained using nanosecond laser excitation. The detected
ion signals for all explosives were shown to be two- to threefold higher in the case of picosecond excitation.
The FAIMS laser desorption regime was developed where a laser beam exiting the detector after removal of a special
plug was used. The results of TNT and RDX detection are presented.
The chip Nd3+:YAG laser has a small emitter and a consumed electric power of 25 W. The estimated detection threshold
of the prototype picosecond laser FAIMS analyzer of explosives is (1-3)∙10-15g/cm3 for TNT vapors.
Double reducing threshold of laser oscillation between two crystals of equal geometry (3x3x10 mm3) and different pump
absorption (80 and 50 %, correspondingly) was observed. For both cases the value of slope efficiency was nearly 22%.
The lowest threshold of absorbed pump power 360 mW with 2% OC was measured for series crystals with small pump
absorption. The focusing of pump beam was no tight (waist radius 38 mm) in comparison with similar experiments with
The technology for manufacturing active elements for high-power (more than 1 kW) Yb3+:YAG disk lasers has
been developed. A series of disk active elements with a thickness of 200...400 μm, a diameter of 8...15 mm, and a Yb3+concentration of 8...15 at. % has been created. A model of a CW disk laser with an output power of 45 W, an optical
efficiency more than 45%, and a pump power density more than 2.5 kW/cm2 has been made.
We demonstrate and optimize, for a mJ/ns release, the operation of a compact laser system designed in the form of a hybrid Q-switched Nd3+:YAG/Cr4+:YAG microchip laser seeding an Yb-doped specialty (GTWave-based) fiber amplifier. A gain factor as high as ~25 dB is achieved for nanosecond single-mode pulses at a 1-10-kHz repetition rate as the result of optimization
New laser transition for 5.5 μm wavelength range was discovered in the moisture-resistant Dy3+:RbPb2Cl5
crystal. Pulse oscillation in free running mode was obtained under YAG:Nd laser pumping at 1.3 μm. Lasing
slope efficiency was as high as 1% at room temperature. In line with our knowledge it is the longest laser
wavelength for a rare earth doped crystal which does not require any special precautions to be survived.
1 mJ pulse energy with a pulse duration less 300 ps was achieved in Nd+3:YAG/Cr+4:YAG microchip laser. To overcome
the polarization instability an output coupler sensitive to polarization was designed, using a multilayer dielectric mirror
evaporated on a substrate made of a birefringent calcite crystal. Reflection coefficients for ordinary and extraordinary
beams Ro = 53% and Re = 57% were obtained. Subnanosecond laser operating at 1064 nm, 532 nm and 355 nm wavelengths with high output brightness and intensity was constructed.
A robust technique for achievement 1 GW output power at O64 nm by amplifying the radiation of diode pumped
YAG:Nd+3/YAG:Cr+4 microchip-laser in flash lamp pumped amplifier is demonstrated. Compact hybrid laser system
with diode pumped microchip master oscillator and two-pass flash lamp pumped amplifier with 300 ps pulse dutation
and 300 mJ output energy operating at repetition rate up to 50 Hz is developed. Features of the laser system design are
Dynamics of the Q-switched microchip lasers pulse was investigated in experiment with high space and time resolution.
It was found that spatial dynamics of the YAG:Nd3+/YAG:Cr4+ microchip laser emission could not be described by
traditional formalism of transverse cavity modes. An alternative theoretical approach based on solution of the Maxwell
scalar wave equation is presented. In our model we take into account the D2d local symmetry of the Cr4+ ions and the
corresponding two types of saturable transitions.
A technique of direct writing of depressed cladding waveguides by a tightly focused, femtosecond laser beam in laser crystals has been developed. A laser based on a depressed cladding waveguide in a Neodimium doped YAG crystal has been demonstrated for the first time.
High efficiency OPO has been designed for converting 1064 micrometers laser radiation into eye-safe region. Conversion efficiency 56.5% and threshold energy 2 mJ (0.06 J.sm2) have been achieved at repetition rate 12.5Hz. The divergence was less than 4 mrad up to 4 thresholds. With 180 mJ pump energy this converter can produce 70mJ output with efficiency 41% and low divergence at repetition rate 2.5Hz.
The technology of producing interference coatings for nonlinear crystals has some peculiarities depending on certain properties of such crystals. Besides, the otpical properties of these coatings depend on laser beam irradiation, temperature, and intracavity or extracavity conditions. Temperature in the vacuum chamber, reactive gas pressure, energy of charged particles, conditions of evaporated materials influenced not in the same way as on usual substrates. It was noted that the ion beam acted on pure surfaces of crystals improving adhesion and reducing mechanical stress of the dielectric film. The ion beam sources were used for pre-cleaning just before deposition as assistance in the deposition process. Adhesion, mechanical stress and laser damage threshold depend on the ion beam energy. The optical properties of pure and coated crystals were tested in relation to the ion beam energy. The threshold has been defined. Besides, the degradation of films has been investigated after exposure to the laser beam. Undoubtedly, the antireflection coatings are of the most interest for such crystals. In this work the following aspects of the Ar coatings have been considered: (i) calculation of the optimum construction of optical coatings for a specific spectral range; (ii) production of the required parameters of the films; (iii) study of the optical parameters; (iv) influence of the ion beam on the spectral characteristics of the AR coatings for LBO and BBO crystals. It was noted that only monoenergetic low-energy beams can improve the optical properties for these crystals having AR coatings. As a result of this work, the AR coatings have been produced at one, two or three wavelengths simultaneously.
The obtaining and investigations of interference coatings in deep ultra violet at 193 nm for medical applications are considered. For successful using in excimer medical system each optical elements must have anti-reflective or high- reflective interference coatings that can be satisfied to medical setup. The general problem is how to produce the event distribution of primary laser irradiation at the nearest distance from eye behind the optical system with minimum losses. Besides all types of coatings must provide a high strength under laser irradiation. The conditions of producing interference coatings in this spectral region have some peculiarities: a limiting factor of the evaporation materials, film homogeneous along the surface of optics, and high laser strength. The processes of interaction between excimer laser photons and optical coatings influenced both on substrate and on film. In this connection the optical properties of some evaporated materials and pure substrates are observed. All films were produced by electron-beam evaporation. Optical absorption and laser strength of coated optics was analyzed as influence and variations of energies of ion-beam source.
Free-running generation performance of a flashlamp-pumped Cr:LiSAF rod are presented. Laser average powers of 14 W at 10 Hz repetition rate, total laser and slope efficiencies of 3.5 percent and 5.1 percent, respectively, have been achieved. the laser was tuned from 810 to 910 with only one pair of broad band mirrors and a birefringent filter in the cavity.
Free-running and Q-switch performance of a flashlamp-pumped Cr:LiSAF laser system have been investigated for repetition rate of 1 - 25 Hz. Laser average powers of 25 W and output pulse energy more 0.1 mJ with 80 ns pulse duration, total laser and slope efficiencies of 5.1% and 3.5%, respectively, have been achieved.
The results of obtaining and investigations coated optics in deep ultra violet (UV) at 193 nm are considered. For successful using in excimer lasers and medical systems the separate optical elements must provide either a good transmission for laser irradiation or enough high reflection. This can be achieved by anti-reflective (AR) or high- reflective (HR) interference coatings. Numerical design and obtaining of UV dielectric coatings are strongly influenced by the material properties in this wavelength region, that differ from those in visible and near infrared. The peculiarities for thin films in this region are: a limiting factor of the evaporation materials, homogeneous along the surface of optics, and high laser strength. The interaction between excimer laser photons and optical coatings can be determined as two combined process of high repetition rates and high energy densities. These processes influence both on substrate and on film. In this connection the investigations of optical properties of oxides (Al2O3, SiO2) and fluoride (MgF2) films are observed. Besides some new aspects in investigation of pure substrates are obtained. All films were produced by electron-beam evaporation and ion-beam influence was analyzed as variation of optical absorption and laser damage threshold (LDT) of coated optics.
Recently much success has been achieved in the field of dielectric interference coatings. However, the appearance of new types of lasers (for example, diode-pumped solid-state lasers) required development of the high quality low loss coatings for various spectral regions. These coatings may be divided into two groups, antireflective coatings and cut-off filters. We have investigated the various aspects of these coatings. There are choice of the optimum construction of the optical coatings to obtain the required parameters in the specific spectral region, development of the production process to obtain the reproducing results when assembling lasers, study of optical parameters. As a result, the technology for making the following coatings has been developed: (1) the AR coatings for Nd:YAG crystals with the coefficient of residual reflection ((rho) ) less than 0.1% of one surface at 1.06 micrometer; (2) the AR stable coating for LiJO3 crystals with the same parameters; (3) the AR coating for KTP crystals with (rho) less than 0.1% of one surface at 1.06 and 0.53 micrometer simultaneously; (4) the AR coating for the BK-7 substrates with (rho) less than 0.3% at 0.809 and 0.53 micrometer simultaneously; (5) the cut-off filter for the BK-7 or Nd:YAG crystal with high reflection (HR) greater than 99.9% at 1.06 micrometer and high transmission (HT) greater than 95% at 0.809 and 0.53 micrometer; (6) the cut-off filter with HR greater than 99.9% at 1.34 micrometer and HT greater than 95% at 0.67 micrometer; (7) the cut-off filter with HR greater than 99.9% at 1.08 micrometer, HR greater than 90% at 0.53 micrometer and HT greater than 85% at 0.355 micrometer. All types of the optical coatings have been tested in the assembly of the lasers. Now these coatings are successfully used in the commercial lasers.
Some aspects of obtaining high reflective (HR) dielectric mirrors with high damage threshold (LDT) for high-power solid-state near IR region (NIR) lasers are considered. Optical properties of these mirrors were investigated as properties of each alternate layer evaporated with high- index (H) or low-index (L) materials as multilayer system that depends on mirror construction, parameters of evaporation, ion-beam influence, substrate materials and quality of substrate surface. Refractory oxides ZrO2,HfO2, Ta2O5, Al2O3 and SiO2 were used as starting materials for evaporation. Ion-beam influence was estimated as changing of optical absorbance at a wavelength 1.064 micrometers by laser modulated photo-thermal radiometry. Besides the quality of various work-up substrate surface was controlled by this method also. It was noticed that substrates with different surface roughness had different absorption. It was noticed that band edge of absorption of pure substrate in UV region influenced on laser damage threshold of mirrors. Optical properties of evaporated mirrors were tested as the ability of strength for laser irradiation as cavity-mirrors of high power lasers. ZrO2/SiO2 mirrors had the most high laser strength. Estimated value of laser density was 3.6 GW/cm2.
The technology of obtaining the interference coatings for the nonlinear crystals has some peculiarities depending on the specific properties of these crystals. Temperature, pressure of reactive gas and energy of charged particles do not affect principally the optical properties of the nonlinear crystal. In this paper the various aspects of thin dielectric films for crystals are presented. There are calculations of the optimum structure of the optical coating for specific spectral region, obtaining the required parameters of the films having the optical properties that would not impair the own properties of the crystal parameters of the films having the optical properties. As a rule, the coatings of these crystals that could be coated without heating in a vacuum chamber. As the result of this work the various types of the interference coatings have been obtained. There are the AR coating at a single wavelength in the spectral range of 0.24...1.5 micrometers , the broad-band AR coatings, the AR coating with two AR spectral regions simultaneously.
The appearance of new types of lasers (for example, diode- pumped solid-state lasers) required development of the high quality low loss coatings for various spectral regions. These coatings can be divided into following groups: antireflective, high-reflective and cut-off filters. Various aspects of producing these coatings have been investigated. There are choice of the optimum construction of the optical coatings to obtain the required parameters in the specific spectral region, development of the production process to obtain the reproducing results when assembling lasers, study of optical parameters. All types of the optical coatings have been tested in the assembly of the lasers. Now these coatings are successfully used in the commercial lasers.
The results of obtaining and investigations coated optics in deep ultra violet (UV) at 193 nm are considered. For successful using in excimer lasers and medical systems the separate optical elements must provide either a good transmission for laser irradiation or enough high reflection. Numerical design and obtaining of UV dielectric coatings are strongly influenced by the material properties in this wavelength region. The peculiarities for thin films in this region are: a limiting factor of the evaporation materials, homogeneous of the film along the surface, and high laser strength. The interaction between excimer laser photons and optical coatings can be determined as two combined process of high repetition rates and high energy densities. These processes influence both on substrate and on film. In this connection the investigations of optical properties of oxides and fluoride films are observed. Besides some new aspects in investigation of pure substrates are obtained. All films were produced by electron-beam evaporation and ion-beam influence was analyzed as variation of optical absorption and laser damage threshold of coated optics.