Flashlamp-pumped Tunable Dye Laser Research Articles

Hypertrophic scarring resulting from flashlamp-pumped pulsed dye laser surgery

The flashlamp-pumped tunable dye laser represents a major advancein the treatment of port-wine stains and other vascularmalformations.' Its superiorityoverpreviously available laser therapy (both carbon dioxide and argon) has been clearlydemonstrated,withsignificant or completefadingoflesions, eveninchildren.' Previous experience with the carbon dioxide and argon lasers has demonstrated that, although effective in most instances these lasers have a significantly higher risk of hypertrophic scarring than that reported with the flashlamppumped tunable dye laser.' The flashlamp-pumped tunabledye laserwasdesigned to minimize these and other risks. Its 577 or 585 nm wavelength corresponds to the beta absorption peak of ~xy'hemoglobin, a wavelength at whichmelaninhas only limitedabsorption, In addition,its 450 msecpulseduration is significantly less than the thermal relaxation time

Incendiary Potential of the Flash-Lamp Pumped 585-nm Tunable Dye Laser

The recently introduced pulsed flash-lamp pumped tunable dye laser is used to treat cutaneous port-wine stains. In our practice, infants and children receive general anesthesia for these brief, yet painful, treatments. Because the flammability of this laser has not been reported and because we administer supplemental oxygen and nitrous oxide, we analyzed the incendiary potential of this laser by measuring the flammability of gauze and Telfa strips, hair, clear plastic face masks and tracheal tubes, and green nasal cannulae in 21%-100% oxygen and in nitrous oxide at laser energies between 6.0 and 10.0 J/cm2. (Our clinical range is 6.0-7.0 J/cm2.) In room air, gauze, Telfa, masks, and tubes did not ignite; only gauze ignited at high energy in 100% oxygen. Hair ignited in room air only when struck repeatedly at high energy, but easily ignited in 100% oxygen. Wetting hair with saline prevented ignition in room air and decreased flammability in supplemental oxygen. Green nasal cannulae prongs were extremely flammable in oxygen. Caution should be taken when using supplemental oxygen/nitrous oxide during treatment with the tunable dye laser.

Acoustic and plasma‐guided laser angioplasty

The feasibility of using acoustic and plasma-guided laser (APGL) for angioplasty was studied in vitro. A flashlamp-pumped tunable dye laser operating at a wavelength of 504 nm (coumarin green) was used as the laser source. Acoustic signals were recorded with a hydrophone, which has a useful frequency response of up to 350 kHz. Plasma optical emissions were transmitted retrograde along the laser fiber and reflected through a beam splitter to an optical detection system consisting of a series of spectral filters (to transmit plasma radiation from 380 nm to 440 nm and block any 504 nm laser light) and a photomultiplier tube. Measurements of the acoustic and the plasma optical signals were obtained from blood, atheromatous plaque, and normal arterial wall. Results of monitoring show that it is possible to know without direct vision whether the laser energy is being discharged in the lumen (blood), on the normal arterial wall, or on the atheromatous plaque. Blood produced strong acoustic signals but no plasma signals; plaque produced strong plasma and strong acoustic signals. Neither plasma nor significant acoustic signals were produced by the normal arterial wall. These distinctions may allow clinical laser ablation of plaque to be performed with fewer complications.

Cellular effects of the pulsed tunable dye laser at 577 nanometers on human endothelial cells, fibroblasts, and erythrocytes: an in vitro study.

The 577-nm flashlamp-pumped tunable dye laser pulsed at 450 microseconds is rapidly becoming the treatment of choice for removal of portwine stains and other vascular ectasias. In this study, we examined the mechanisms of vessel destruction by determining the effects of laser irradiation on three types of primary target cells--erythrocytes, endothelial cells, and fibroblasts. Human endothelial cells and fibroblasts in microwell plates were irradiated at various energy densities with the laser, after which several aspects of cellular biology were determined, including 1) viability of cells by trypan blue exclusion test; 2) cell proliferation by [3H]thymidine incorporation; and 3) rate of protein synthesis using [3H]leucine incorporation as a marker. In endothelial cell cultures, both [3H]thymidine and [3H]leucine incorporations were inhibited at energy levels of 5-12 J/cm2 (P less than 0.01). In fibroblast cultures, cell proliferation was similarly inhibited, while supratherapeutic energy density (greater than or equal to 12 J/cm2) was required for inhibition of protein synthesis. The laser energy in the range of 5-8.5 J/cm2 had no effect on cell viability. Erythrocytes as target cells for laser energy demonstrated rapid, dose-dependent lysis, as determined by release of free hemoglobin into culture medium. Addition of erythrocytes into a coculture with endothelial cells abolished the direct inhibitory effect noted in cultures when endothelial cells were present alone. The results of the latter experiment imply that erythrocytes are the primary target cell absorbing the laser energy at 577 nm. However, direct laser effects on endothelial cells may also contribute to the mechanisms of ablation of the vascular ectasias by the tunable dye laser at 577 nm.

5-J 18-μsec pulse 10-pps dye laser for combustion applications

A 5-J/pulse 1.8-microsec pulse width 10-Hz flashlamp-pumped tunable dye laser system has been built for performing spontaneous Raman scattering experiments in combusting media at the Combustion Research Facility, Sandia National Laboratories, Livermore. Details of construction, including a microprocessor-based diagnostic and control system, are described, and performance of the system in terms of various operating parameters is noted.

General purpose microcomputer-based data acquisition and laser control circuitry for use in one-photon and two-photon laser spectroscopy

Four general purpose circuits are described which facilitate computer control and synchronization of laser firing, analog-to-digital conversion, and digital-to-digital multiplexing. These circuits retain generality by using only the 16 input and output lines of the computer interface without utilization of handshaking or data request lines. Accordingly, these circuits can be used with any 16-bit TTL interface that provides latched output lines. The generality is obtained at the expense of data transfer and control speed and with a loss of interrupt capability. An analog-to-digital converter circuit is described which provides eight computer selected input channels, 12-bit resolution, and a total cycle time for each input reading of ≈60 μs. Each input channel can be independently set to generate a full scale reading for 0.1, 1, or 10 V inputs. A pulse conditioning trigger circuit is described which generates an output pulse of selected delay (50 ns–2 ms), pulse width (30 ns–2.5 ms), and magnitude (up to 10 V) in response to a computer-generated positive going TTL pulse. Applications of the above circuits in controlling and acquiring data from a two-photon laser spectrometer are discussed. A 28-bit to 16-bit digital multiplexer circuit is described which can be used to input data using a 16-bit computer interface from instruments with data words up to and including 28 bits. The EG&G Princeton Applied Research (PAR) model 4202 transient signal averager and the PAR model 1205A optical multichannel analyzer are discussed as examples. Finally, a laser firing circuit specifically designed to provide one-shot triggering of the Chromatix CMX-4 flashlamp-pumped tunable dye laser is described. The unique external triggering requirements of the CMX-4 require a 10-V pulse of 8.34±0.01 ms duration to generate reliable triggering.

Laser excitation spectrum of PbO: Rotational analysis of the a(1)- X(0 +) system

A flashlamp-pumped tunable dye laser has been used to investigate the a- X band system of PbO. Spectra with resolution adequate for rotational analysis were obtained by exciting a- X photoluminescence with the laser operating at a bandwidth of 0.2 cm −1. The (3,1) and (4,1) bands have been rotationally analyzed, providing the rotational constants B 3 = 0.2389 ± 0.0002 cm −1 and B 4 = 0.2374 ± 0.0002 cm −1 for the a state. Observation of P, Q, and R branch structure confirms the assignment of the a state as a Hund's case ( c), Ω = 1 state of PbO. Calculated combination defects having positive algebraic sign support the presence of a b(0 −) state approximately 350 cm −1 above the a(1) state.

Application of laser-excited atomic fluorescence spectrometry to the determination of iron

A frequency-doubled, flashlamp-pumped tunable dye laser is used to excite the Stokes direct-line atomic fluorescence transition of iron (296.7 nm/373.5 nm). Limits of detection are determined with single (0.6 ng/ml) and multipass (0.2 ng/ml) and with a l s time constant (a 0.06 ng/ml limit detection is obtained with an 8 s time constant). Noise sources limiting precision at both low (background flame emission shot and flicker noise) and high concentrations (laser pulse to pulse variability) concentrations are investigated and the technique is used for the determination of iron in simulated fresh water NBS SRM-1643), unalloyed copper (NBS SRM-394) and fly ash (NBS SRM-1633).

Two-photon excitation of Na atoms in a flame by broad-band laser irradiation

With a flashlamp-pumped tunable dye laser the 3 S→3 D, 3 S→4 D and 3 S→5 S two-photon transitions of sodium are excited and the resulting fluorescence radiation at various atomic transitions is detected. The sodium is nebulized into a stoichiometric H 2-O 2-Ar flame at atmospheric pressure and at a temperature of 1800 K. Collisional population exchange between several of the higher Na-levels is found to occur. Saturation and saturation broadening of two-photon transitions are observed. Formulas for two- photon excitation rates in the case of broad-band excitation are derived and show substantial agreement with experiment.

Dye laser pumped atomic iodine laser

Lasing has been demonstrated on the 2P1/2–2P3/2 transition in atomic iodine by optically pumping I2 vapor to dissociation with a flashlamp-pumped tunable dye laser. Lasing at 1.315 μ has been observed for pump wavelengths from 5010 to 4930 Å. The device holds promise as a rapidly pulsed gain diagnostic for existing or future iodine systems.

Yields of Br* (4 2P [formula omitted]) as a function of wavelength in the photodissociation of Br 2 and IBr

A flashlamp-pumped tunable dye laser has been used to study the photochemical production of Br* (4 2P 1 2 ) atoms from Br 2 and IBr exc

Photodissociation of negative ions formed in CO2 and CO2/O2 mixtures

A new tandem quadrupole mass spectrometer, developed explicitly for photodissociation experiments, has been used to study the photodissociation reactions of CO3− and CO4− ions formed in CO2 and CO2/O2 mixtures at pressures between 0.05 and 1.4 torr. These measurements have been accomplished at six discrete photon energies between 2.1–4.1 eV using the intense lines from a 200 W Hg lamp with a small monochromater, and more detailed measurements were carried out between 1.8–2.1 eV using a flash-lamp pumped tunable dye laser. The apparent photodissociation cross section for the reaction CO3−→O−+CO2 was measured as a function of ion source pressure at several wavelengths. The results are interpreted as indicating that CO3− ions produced by the three-body association reaction, O−+2CO2→CO3−+CO2 are initially formed in an electronically excited state and are rather slowly relaxed to the ground state by further collisions with CO2. The measured relaxation rate constant is approximately 5×10−14 cm3/sec.

Tuning properties of flashlamp-pumped dye lasers with dye mixtures

This note reports the experimental result of lasing properties if a flashlamp-pumped tunable dye laser having a mixture of xanthene and a cridine dyes. The lasing threshold energy of the dye mixtures in the methanol solution decreases considerably and the lasing wavelength shifts to the long wavelength side over about ten or more nm in comparison with the tuning range of the pumping dye. In the ethanol solution, however, these phenomena are not observed.

Fast resonance raman spectroscopy of short-lived radicals

We report the first application of pulsed resonance Raman spectroscopy to the study of short-lived free radicals produced by pulse radiolysis. A single pulse from a flash-lamp pumped tunable dye laser is used to excite the resonance Raman spectrum of the p-terphenyl anion radical with an initial concentration of 4 × 10 −5 moles per liter and a half life of 2 μs. The spectrum is recorded by an optical multichannel system consisting of an image intensifier coupled to a TV-camera.

The spectral linewidth of a flashlamp-pumped dye laser

The rate equations for the molecular state densities and mode photon densities are set up for a flashlamp-pumped tunable dye laser. These are solved numerically for a typical rhodamine 6G laser tuned by a Fabry-Perot etalon and the results compared with experiment. The untuned dye laser line shape is also calculated and compared with experiment.