Laser Pulse Compression & Stretching
Highly effective compression and stretching of picosecond and femtosecond laser pulses can be accomplished by using matched pairs of Volume Phase Holographic Gratings (VPHGs) in transmission geometry. As shown in the figure below, compression and stretching is proportional to the distance between the parallel gratings. A mirror can be inserted to double the dispersion and/or two identical lenses can be placed two focal lengths apart for compression purposes.
Example Graph Below of 1213 lpmm grating (70.1 degrees) for 1550nm
Energy Density Information
We are collecting energy density data from various pulsed laser companies. Energy density failure is a mostly a function of the glue/gelatin/glass assembly with the glue usually failing first by softening. Below is information typical of a successful medical pulsed laser application. Continuous wave (CW) energy densities of up to ~10 watts/cm^2 are fine; up to ~100 10 watts/cm^2 is possible with suitable epoxies.
|Energy Density Measurements (approximate) from Customers
|Description||Application #1||Application #2||Application #3|
|Pulsed Laser Type||1054nm, S polarized||
800nm, P polarized
|530nm, P polarized|
|Pulse Duration||500 fs||130 fs||<200 fs|
|Repetition Rate||>10 KHz||1 KHz||1 KHz|
(Energy/pulse X Repetition Rate )
|>300 mW||>300 mW||>7 mW|
|Average Power Density
(Average Power / Beam Area)
|>1.5 Watts/cm2||>5 Watts/cm2||0.5 Watts/cm2|
((Energy/pulse) / Pulse Duration)
|6×10^7 Watts||3×10^9 Watts||>3×10^7 Watts|
|Peak Power Density
(Peak Power / Beam Area)
|3×10^8 Watts/cm2||4×10^10 Watts/cm2||2×10^9 Watts/cm2|
|Test Duration||In commercial use||1.5 hours with no failure||Preliminary|
External Cavity Laser Tuning
External cavity diode and dye lasers can be spectrally tuned and made to operate in a single-mode. Light exiting from the laser cavity diverges, passes through a collimator, and is imaged on a grating. In Littrow and Littman configurations, the grating is positioned so that light of the correct wavelength is redirected back through the collimator and focused into the laser cavity. Gratings for single or dual polarizations can be produced.
Littman System Using VPH Transmission Gratings, S (TE) Maximized
Grating Enhanced External Cavity Laser Diode (GEECLD): Graphs & diagrams courtesy of Andreas Wicht, University of Dusseldorf
- Tunable Diffraction Efficiency (>90%): High diffraction efficiencies are helpful to detune the laser far away from gain maximum. Alternatively, to circumvent the gain maximum, especially at high currents, lower diffraction efficiencies are preferred.
- Higher Spatial Frequencies (=> More Compact): In all Littman diode setups, transmission gratings allow the application of line densities which are about twice as large as for reflection gratings. This is because the first order is diffracted back into the laser diode, and not at ~90 degrees with respect to the incident beam.
- Maximum Diffraction Efficiency: Higher efficiency than commercial reflection gratings.
- Continuous Tuning Over A Wide Band
Stock: Dual Polarization VPH Transmission Gratings: AOI=AOD
|Stock: Dual Polarization VPH Transmission Gratings: AOI=AOD|
|AOI/AODat CWL||S & P Efficiencies|
|Custom VPH Transmission Gratings: >90% Efficiencies
These VPHGs can be customized for almost any wavelength or spatial frequency, are environmentally rugged, and scratch resistant. Process Instruments uses of our volume phase holographic gratings for their diode laser systems.
We provide a high level of customer service. Additionally, we offer consulting, design, prototype, product integration, and quantity production at competitive prices. For sales info contact 435-752-4301, email us, or send us a completed Customer Grating Worksheet.