Infrared saturable absorbers. Part II: Intensity dependent transmission of SF6 at 936.8 wave numbers

1977 ◽  
Vol 55 (18) ◽  
pp. 1569-1579
Author(s):  
George F. Caudle ◽  
Jerald R. Izatt ◽  
Tuan-Kay Lim
Keyword(s):  
Cross Sections ◽  
Average Power ◽  
Excited State Absorption ◽  
Laser Pulses ◽  
Beam Power ◽  
Hole Burning ◽  
Saturable Absorbers ◽  
Pulse Transmission ◽  
Band Absorption ◽  
Level Model

Due to rotational hole burning Q-switched laser pulses sometimes saturate a molecular absorber more effectively than CW laser radiation. The absorption by SF6 of frequencies near the P(28) line in the 10.6 μm CO2 laser band provides an interesting example. In this case it has been reported elsewhere that for peak intensities [Formula: see text] an increase in pulse intensity produces a monotonic increase in transmission whereas the CW transmission decreases monotonically with intensity. We report new measurements made over a wider range of laser power levels and at several SF6 pressures, which show that the global behavior of the transmission as a function of average beam power is quite similar for both CW and pulsed radiation. The pulse transmission is somewhat greater at all power levels, but when the average power is sufficiently high the growth of hot-band absorption and possibly other intensity dependent changes in the ground and excited-state absorption cross sections cause the transmission to fall well below its low-intensity value for CW radiation and pulses alike. The experimental transmission curves for both cases display as many as three extrema and cannot be explained, even qualitatively, by the five-level model used in the earlier work. The extended results are consistent with the modified five-level model presented in Part I of this pair of papers.

Wavelength Dispersion of Optical Power Limiting in Stilbene3 Analyzed within a Three Level Model

1999 ◽  
Vol 597 ◽  
Author(s):  
P-A. Chollet ◽  
A. Somin ◽  
B. Paci ◽  
V. Hully ◽  
J-M. Nunzi ◽  
...  
Keyword(s):  
Excited State Absorption ◽  
Optical Power ◽  
Laser Pulses ◽  
Optical Limiting ◽  
Photon Absorption ◽  
Visible Range ◽  
Nanosecond Laser ◽  
Nonlinear Transmission ◽  
Two Photon ◽  
Level Model

AbstractNonlinear transmission in a dye (stilbene3) exhibiting two-photon absorption (TPA) has been studied has a function of wavelength, in the visible range using nanosecond laser pulses. The results have been analyzed within a three level model: the first excited one is populated by TPA and is excited toward an upper level (excited state absorption, ESA). The TPA and ESA spectra obtained by optical limiting (δ∼10-46 cm4s photon-1molecule-1; δ∼ 10-16 cm2) are in good agreement with those determined by two-photon fluorescence and Kerr ellipsometry. Thus, nonlinear transmission appears as a useful technique to estimate the TPA and ESA contributions in optical limiting.

Nonlinear Optical Properties of Modified Carbocyanines

1997 ◽  
Vol 479 ◽  
Author(s):  
Nansheng Tang ◽  
Weijie Su ◽  
Thomas M. Cooper ◽  
Daniel G. McLean ◽  
Donna M. Brandelik ◽  
...  
Keyword(s):  
Cross Sections ◽  
Excited State Absorption ◽  
Laser Pulses ◽  
Saturable Absorption ◽  
Reverse Saturable Absorption ◽  
Pump Probe ◽  
Chirped Pulses ◽  
Molecular Hyperpolarizability ◽  
Meso Position ◽  
532 Nm

AbstractWe studied the optical nonlinearities of modified 3,3′-diethylthiadicarbocyanine iodides (X-DTDCI) in dimethyl sulfoxide (DMSO) solutions (X = H, Cl, Br at meso position) by a pump-probe technique with crossed polarized chirped laser pulses at room temperature. Reverse-saturable-absorption (RSA) with monoexponential lifetimes is observed at 532 nm in all the samples studied. We determined the effective excited-state absorption cross-sections and their lifetimes for all the samples investigated and found that they clearly correlate to the substituent X at the meso position. Empowered by the chirped pulses, a much faster nonlinearity with a decay time of ˜3.1 ps that is much shorter than the laser pulses used, is unveiled in Cl-DTDCI. We expressed both the absorptive and the refractive part of this fast nonlinearity as the equivalent molecular hyperpolarizability γ1212 and found γ1212 = (8.1 + i9.8) × 10−32erg−1.

Wavelength dependent studies of nonlinear absorption in zinc meso-tetra(p-methoxyphenyl)tetrabenzoporphyrin (Znmp TBP) using Z-scan technique

2001 ◽  
Vol 05 (07) ◽  
pp. 549-554 ◽  
Author(s):  
N. K. M. NAGA SRINIVAS ◽  
S. VENUGOPAL RAO ◽  
D. V. G. L. N. RAO ◽  
B. K. KIMBALL ◽  
M. NAKASHIMA ◽  
...  
Keyword(s):  
Excited State ◽  
Cross Sections ◽  
Nonlinear Absorption ◽  
Visible Region ◽  
Excited State Absorption ◽  
Photon Absorption ◽  
Dispersion Data ◽  
Level Model ◽  
Scan Data ◽  
Two Photon Absorption Coefficient

We report here, our experimental results and theoretical analysis of the dispersion data of nonlinear absorption in zinc meso-tetra-(p-methoxyphenyl)tetrabenzoporphyrin (ZnmpTBP). Using a ns optical parametric oscillator (OPO) we obtain the open aperture Z-scan data over the visible region starting from 480 nm to 600 nm. We use a more general five-level model for evaluating the excited state parameters like excited state absorption coefficients, two-photon absorption coefficient, etc. Due to its large excited state absorption cross-sections this material acts as a very good candidate for a broadband optical limiter in the visible region.

Some Aspects of the Inverse Problem of Determination of Cr^(4+) :YAG Absorption Cross Sections Using Experimental Data of Transmission

2001 ◽  
Vol 6 (1) ◽  
pp. 39-55 ◽  
Author(s):  
A. Dement’ev ◽  
R. Navakas
Keyword(s):  
Experimental Data ◽  
Inverse Problem ◽  
Cross Sections ◽  
Critical Analysis ◽  
Laser Pulses ◽  
Absorption Cross ◽  
Pump Radiation ◽  
Level Model ◽  
True Values

Mathematical modelling of nonlinear transmission of Cr4+:YAG crystals excited by Nd:YAG laser pulses of different duration are reported. Numerical simulation of transmission using a five-level scheme which included finite excitation lifetimes in Cr4+:YAG, focusing and diffraction of transversely nonhomogeneous pump radiation allowed to specify more precisely the limits of applicability of the four-level model. Critical analysis of typical simplifications commonly used for solving an inverse problem of determination of absorption cross sections is undertaken. It is shown that some of these assumptions that seem plausible enough might lead to considerable deviations of the determined absorption cross sections from their “true” values. A technique for determination of confidence intervals in case of the nonlinear regression is emphasized.

Shortening of excimer laser pulses with saturable absorbers

1984 ◽  
Vol 52 (3) ◽  
pp. 211-214 ◽  
Author(s):  
Ch.G. Christov ◽  
I.V. Tomov ◽  
I.V. Chaltakov ◽  
V.L. Lyutskanov
Keyword(s):  
Excimer Laser ◽  
Laser Pulses ◽  
Saturable Absorbers

Analysis of Silicon Micromachining by UV Lasers, and Implications for Full Cut Laser Dicing of Ultra-Thin Semiconductor Device Wafers

2010 ◽  
Vol 2010 (DPC) ◽  
pp. 001743-001759
Author(s):  
Andy Hooper ◽  
Daragh Finn
Keyword(s):  
Cross Sections ◽  
Laser Scanning ◽  
Semiconductor Device ◽  
Laser Pulses ◽  
Silicon Wafers ◽  
Silicon Devices ◽  
Laser Fluences ◽  
Slow Velocity ◽  
3D Packaging ◽  
Thin Silicon

3D packaging technologies such as FLASH rely on die-to-die stacking of ultra-thin silicon devices with individual die thicknesses below 100 um. Because ultra-thin silicon wafers are very fragile, mechanical saw dicing of sub 100 um thick wafers tends to be more challenging, requiring slower processing and reduced throughput and/or yields. These challenges make full cut laser dicing an attractive solution. This presentation provides an investigation for machining of 50 um thick silicon wafers using a Gaussian-shaped, nanosecond pulsewidth, 355 nm UV laser. A range of machining speeds and laser fluences are compared, from single laser pulses to highly overlapped slow-velocity machining. 3D Laser Scanning Microscope and FIB/TEM cross sections are employed to characterize the state and depth of heating damage into the Si material. Implications for laser machining rates and die break strength are investigated for full cut laser dicing.

Video-Rate Scanning Two-Photon Excitation Fluorescence Microscopy

1998 ◽  
Vol 4 (S2) ◽  
pp. 424-425
Author(s):  
G.Y. Fan ◽  
H. Fujisaki ◽  
R.-K. Tsay ◽  
R.Y. Tsien ◽  
Mark H. Ellisman
Keyword(s):  
Laser Beam ◽  
Group Velocity Dispersion ◽  
Laser System ◽  
Average Power ◽  
Laser Pulses ◽  
Green Laser ◽  
Two Photon ◽  
Photon Excitation ◽  
Schematic Layout ◽  
Two Photon Excitation

A video-rate scanning two-photon excitation microscope (TPEM) has been successfully constructed and tested. The TPEM, based on a Nikon RCM-8000, incorporates a femtosecond pulsed laser, a pre-chirper, and a non-confocal detection box for ratio imaging. Fig. 1 shows the schematic layout of the main components of the instrument, each of which is briefly discussed below.Laser System: A Tsunami Ti: Sapphire laser (from Spectra-Physics) is optically pumped by a 5 W green laser (Millennia from Spectra-Physics) and is capable of generating 100 fs pulses at a repetition rate of 82 MHz and an average power of 0.8 W. The output wavelength is tunable from 690 to 1050 nm with three optical sets, each covering part of the spectrum with some overlapping.Pre-chirper: After leaving the Tsunami, the laser beam enters an optic unit known as a pre-chirper which pre-chirps laser pulses to compensate for the group velocity dispersion which will result when the laser beam goes through the microscope optics.

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