Holographic contouring by using tunable lasers

We report a highly efficient, compact low-cost tunable dye laser pumped directly by green laser diodes. A tunable dye laser quasi-longitudinally pumped by two multimode InGaN diodes (520 nm), was implemented in a 200 ns pulsed mode with a 2 Hz repetition frequency. The lasing threshold energies were found to be 0.23–0.37 $$\upmu \hbox {J}$$ using an output mirror with 13% transmission. The best efficiency at the lasing maximum for Pyrromethene 567 exceeded 25% when the slope efficiency in broadband cavity configuration was 43% at an absorbed pump energy of $$0.75\,\upmu \hbox {J}$$ . The laser overlapped a wide spectral region of 145 nm (from 537 to 682 nm) with a linewidth of 1 nm. This indicates that green diodes can be used as an effective pump source for tunable dye lasers. Such lasers will be useful for spectroscopy, medicine and other fields due to their compactness and low cost.

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant inherited condition that has cutaneous telangiectasia as a component of its manifestations. It has been found that the tunable dye laser is effective in the clearance of these lesions. Twelve patients with HHT between 1991 and 1999 were treated with the tunable dye laser. Treatment was carried out at 3-month intervals. Of the 12 patients treated with the tunable dye laser, 10 were evaluated after treatment. In all cases, the cutaneous component had resolved. The diagnosis of HHT should be considered in all cases of telangiectatic skin lesions. The tunable dye laser appears to be an effective means of resolving any cosmetic problems.

Powerful and tunable lasers in the visible region are expected to be realized in the very near future, for the purpose of laser isotope separation and applications of tunable dye lasers, not only in our country but also in the United States and Europe. However, it is not so easy to realize both high power or energy and good tunability.In this paper, we wish to report an investigation of verious types of high-power tunable dye lasers which can be used as a pumping source for atomic uranium isotope enrichment, and high power techniques of dye laser apparatus, especially flashlamp-pumped high energy dye lasers developed in our laboratory.

Many new effects in optical physics and spectroscopy owe their origin to tunable dye lasers. Even if more practical and efficient tunable lasers are developed in the future, the remarkable role of the dye lasers in the advancement of science and technology cannot be overestimated. I would like to illustrate this statement with the example of the discovery of the methods for manipulating atomic motion by means of laser radiation, particularly the methods of the laserinduced optics of atomic beams. Incidentally, this area of laser-atomic physics will also be twenty five in two years. My interest in this problem was aroused in 1968 in connection with the search for new Doppler-free laser spectroscopic techniques. In the sixties, new Doppler-free laser absorption saturation spectroscopic methods were developed on the basis of the Lamb dip [11.1] and the inverted Lamp dip [11.2]. A shortcoming of this powerful technique is that it is capable of eliminating the linear Doppler broadening only in the quantum transition being saturated and in those coupled to it. I was aware of the fact that a principally different method existed to suppress the Doppler broadening, based on the restriction of the particle's motion within an area less than about 2 (radiation wavelength) across. This effect, referred to as the Lamp-Dicke regime [11.3], was successfully realized in the microwave band in the Ramsey hydrogen maser (storage bulb method) [11.4]. To implement such an approach in the optical region of the spectrum, I suggested [11.5] trapping atoms or molecules in small regions of space, less than ~'opt in size, by means of the so-called spatially periodic gradient force in a standing light wave (Fig. 11.1a). Thanks to the restriction (localization) of the atomic motion, there should have taken place a severe distortion of the Doppler profile with a narrow peak in its center, of all spectral lines observed along the axis of the standing light wave. I believed this method to hold much promise for high-resolution laser spectroscopy (in addition to saturation spectroscopy [11.1, 2] and two-photon spectroscopy in counter-propagating waves [ 11.6]) and called it the spectroscopy of trapped particles [11.7]. However, this idea, attractive as it was, could not be carried into effect without tunable lasers. I remember how, at the beginning of my research work at the Institute of Spectroscopy, Dr. O. Kompanets and myself made an attempt to

Interaction of some organic dyes with DNA induces fluorescence enhancement through intercalation or groove binding, stimulating the development of compact tunable thin-film dye lasers. We have demonstrated amplified spontaneous emission (ASE), laser emission and its tuning via distributed feedback (DFB) with a dynamic grating formed in DNA-surfactant complexes doped with cyanine or hemicyanine dyes. The formation of semi-persistent (or quasi-dynamic) grating is more preferable in order to realize stable and easily tunable laser sources, so we fabricated bi-layered devices composed of a DNA-CTMA layer doped with pyridine 1 (Py1) and an PMMA layer including an azo dye, Disperse Red 1 (DR1). Under simultaneous excitation of the azo layer with interfering two beams for grating formation and the emission layer with another beam as pumping, we observed laser emission from the device. The oscillation wavelength was controlled by varying the incident beam angles allowing the fast tuning suitable to applications. Furthermore, monolithic DNA device having two functions of lasing and grating formation would be more promising. DNA-CTMA complex had been considered to be a poor matrix for grating inscription, but we found that doping of an azo-carbazole compound made it possible to inscribe gratings with relatively high diffraction efficiency and with fast response which could be applicable to monolithic tunable laser system.

Ultrastructure: Effects of Melanin Pigment on Target Specificity Using a Pulsed Dye Laser (577 nm)

A compact, high-peak-power, user-friendly, single-longitudinal-mode (SLM) tunable dye laser has been developed. The device yields ≳12 mJ pulses of 6 ns duration and ∼2.7×transform-limited linewidths of <200 MHz. Seamless single-mode tunability of ≳20 cm−1 is possible without resetting. The dye laser makes efficient use of the pump laser, with ∼10% conversion of the 532 nm pump energy to tunable dye power and occupies <4 m2 (including pump laser and all diagnostics). The linewidth of the device can be switched from <200 MHz SLM operation to <0.5 cm−1 broadband modeless operation by moving one mirror. This allows rapid interchange between high-resolution scanning and a ‘‘fast survey scan’’ mode of operation to isolate the spectral region of interest at low resolution.

A tunable organic dye laser has been used as a narrow band (∼0.8 Å) radiation source to excite NO2 molecules under essentially collision-free conditions in the spectral range 4515–4605 Å. The fluorescence which is observed in a very large cell is decidedly nonexponential, so that the decay function for each experiment is characterized as both nonexponential and exponential, the latter for purposes of comparison with other experiments and for purposes of discussion in standard terms. The lifetimes which are obtained in this way show a marked structural pattern when displayed as a spectrum, with individual values ranging from 62 to 75 μsec for observation of fluorescence at wavelengths longer than 5200 Å. In addition, the dependence of lifetime and nonexponentiality, as well as their spectral variations, on observation wavelength, pressure, and fluorescence observation geometry are investigated over a shorter spectral region. A small amount of high resolution spectral data is reported which seems to indicate the presence of some unresolved, quasicontinuous absorption underlying the obvious bands of the visible spectrum. The effects of restrictive fluorescence measurement geometry on lifetime measurements are explored, with particular attention to other investigations, for which the shorter, nonvarying lifetime observations may be explained. Finally the observed dynamics and spectroscopy of NO2 are discussed in terms of the following hypotheses: (1) Transitions to both the 2B1 and 2B2 electronic states occur together over a large portion of the visible spectrum, (2) both of these excited states are clearly perturbed, and (3) the 2B2 transition is the stronger of the two.

A compact disk is used as a dispersive element for spectral narrowing and wavelength tuning in a tunable narrow-band dye laser. The performance of the laser with the compact disk is evaluated and compared with a similar laser system using a research grade diffraction grating.

Organic lasers came into existence via the introduction of the pulsed optically-pumped liquid organic dye laser by Sorokin and Lankard (1966) and Schafer et al. (1966). An additional momentous contribution was the discovery of the continuous wave (CW) liquid organic dye laser by Peterson et al. (1970) which opened the way for the development of narrow-linewidth tunability in the CW regime plus the eventual introduction of femtosecond lasers (see, for example, Dietel et al. (1983) and Diels, (1990)). The narrowlinewidth tunable pulsed dye laser was demonstrated by Hansch (1972) and improved by Shoshan et al. (1977), Littman and Metcalf (1978), Duarte and Piper (1980, 1981). All these developments in practical organic tunable lasers, spanning the visible spectrum, “created a renaissance in diverse applied fields such as medicine, remote sensing, isotope separation, spectroscopy, photochemistry, and other analytical tasks” (Duarte et al. (1992)). An early development, in the field of tunable lasers, was also the discovery of solid-state pulsed optically-pumped organic dye lasers by Soffer and McFarland (1967) and Peterson and Snavely (1968). However, it was not until the 1990s that, due to improvements in the dye-doped polymer gain media, this class of lasers would again be the focus of research attention (see, for example, Duarte (1994), Maslyukov et al. (1995), Costela et al. (2003)). An additional effort in optically-pumped tunable laser research is the work on organic semiconductor lasers based on thin-film conjugated polymers (see, for example, Holzer et al. (2002)). All this activity has been conducted on optically-pumped organic lasers although researchers from the onset have also been interested on the direct electronic excitation of tunable organic lasers (Steyer and Schafer, 1974; Marowsky et al., 1976). Some recent reviews mentioning efforts towards realizing coherent emission from direct electrical excitation of organic semiconductors, include Kranzelbinder and Leising (2000), Baldo et al. (2002), Samuel and Turnbull (2007), and Karnutsch (2007). Most of these reviews give ample attention to conjugated polymer gain media. In this chapter, experimental results demonstrating coherent emission from electricallyexcited pulsed dye-doped organic semiconductors, in microcavity configurations, are reviewed. The reported emission is single-transverse-mode, and given the 300 nm cavity length, also single-longitudinal mode. In the spectral domain the emission is indistinguishable

Interest in laser isotope separation and laser induced chemistry is now creating a large demand for tunable lasers throughout the frequency spectrum. In the visible and near uv these demands have generally been met with tunable dye lasers and frequency doubled dye lasers. However, development of tunable lasers operative throughout the ir has proven to be much more difficult. The difficulty is greatly enhanced by the strict wave-length requirements dictated by isotope separation. In this presentation the status of various experimental approaches being pursued for solution of this problem will be reviewed. These approaches may be grouped under the general headings of: optical pumping, non linear optics in gases and solids, electrical discharges in gases, and excitation transfer. In addition, because of the large number of known ir laser transitions, there may be near coincidences between a particular line of an existing laser and the desired absorption feature. In this case one would like to have a fine tuning capability that is continuous over a range of ~ ± .5 cm-1 comparable to spacings between rotational lines. Several possible solutions to this problem will also be discussed.

A report is given of the first quantitative study of the spontaneous and stimulated electronic Raman scattering by a resonance doublet of the sodium atom excited resonantly at the D1 and D2 lines by a tunable dye laser. Theoretical and experimental analyses of the differential scattering cross section and polarization properties at the Stokes and anti-Stokes frequencies show that the observed scattering is due to a nearly resonant process involving the ground state 3S1/2 as the dominant intermediate state. The stimulated Stokes and anti-Stokes scattering lines, which are shifted from the D1 and D2 lines by an amount corresponding to the frequency separation between lowest-lying excited doublets 3P1/2 and 3P3/2, are observed by exciting a sodium vapor cell with a passively mode-locked dye laser.

We summarize a research program on remote optical measurements of humidity and temperature and give new results of such measurements as well as new data on the near IR absorption spectrum of H20. The basic atmospheric technique is differential absorption lidar (DIAL) using narrow band, tunable dye lasers. Approximate wavelengths are 720, 820, and 940 nm (H20) and 690 and 760 nm (02; temperature). The requisite absorption line strengths and widths are measured in a controlled environment by means of grating spectroscopy and tunable lasers. Prospects for routine lidar meteorology, even from airplane and satellite platforms, appear excellent. In several important applications, the conditions and the optical properties of the atmosphere can be obtained remotely by these means.

A research program on remote optical measurements of humidity and temperature is summarized, and new results are given of such measurements as well as new data on the near IR absorption spectrum of H2O. The basic atmospheric technique is differential absorption lidar (DIAL) using narrow band, tunable dye lasers. Approximate wavelengths are 720, 820, 940 nm (H2O) and 690, 760 nm (O2; temperature). The requisite absorption line strengths and widths are measured in a controlled environment by means of grating spectroscopy and tunable lasers. Prospects for routine lidar meteorology, even from airplane and satellite platforms, appear excellent in several important applications; the conditions and the optical properties of the atmosphere can be obtained remotely by these means.

In this chapter, some other tunable lasers will be briefly introduced, such as tunable dye laser, stimulated Raman laser, fiber Raman laser, and so on. These tunable technologies and theory still can be used for many fields, for example, laser radar, chemical reaction, biology, holography, medicine, nonlinear optics, etc.