Advanced Laser Light Source (ALLS)

Université du Québec

ALLS/LSF (Advanced Laser Light Source/ Laboratoire de Sources Femtosecondes) is a unique infrastructure of international caliber located at the Varennes campus of INRS-EMT (20 minutes south-east of Montreal), where users can find a variety of intense ultrafast laser sources. This large national laboratory for laser science was financed through the "International Joint Ventures Fund" program of the Canada Foundation for Innovation (CFI) with an investment of 20.95M$. With the powerful lasers at the ALLS lab a series of new ultrafast light sources for revolutionary applications has been developed.

Subsequently, this laboratory achieved the development of a large variety of laser light sources reaching from THz (300 micron wavelength) to hard X-rays (Angstrom – 0.1 nm wavelength) providing ultra short pulse durations. Since these light sources are generated in an all-optical way, light pulses of different wavelengths can be spatially and temporally synchronized . This opens the door to explore the potential of dynamic imaging of atomic, molecular and condensed matter systems and provides the unique tools to explore the fundamental questions of physics and chemistry. This leads to important outcome in fundamental science as well as in innovative technological applications and tools. Among them are medical high resolution imaging for mammography and particle acceleration for future proton therapy, micro machining and material processing, as well as applications for security and defense, telecommunication and information.

The high‐energy infrared beam‐line at the Advanced Laser Light Source (ALLS)

This infrared beam‐line is derived from a commercial 100Hz CPA Ti:Sa laser system delivering 800nm ultrashort pulses with 40 fs pulse duration after compression with a repetition rate of 100 Hz. Two independent compressors are available at the output. A low energy compressor is delivering up to 5 mJ to pump OPA1. This OPA delivers tunable infrared pulses at mJ level. Then, this OPA output is spatially filtered and seeds a following high‐energy 22x22mm OPA stage (OPA2). To pump this stage, the high energy compressor of the laser system delivers up to 45 mJ at 800 nm. The beams can be coupled to either one of the two fixed hollow‐core fibers to achieve pulse compression down to few‐cycle regime, or to generate mid‐infrared pulses tunable from 3 to 12 microns (energy range from 10 to 100 microjoules).

infrared beam-line diagram

Specifications of the infrared beamline

 

   Wavelength   
(nm)

  Pulse duration  
(fs)

  Energy per pulse  
(mJ)

  Compressor 1   800 40 5
  Compressor 2   800 40 45
 OPA 1 1200-2100 50 0.8
OPA 2 1200 - 2100 50 5
Fiber   800, 1400, 1800   7-15 0.5-3
Mid-infrared 3000 to 12000 sub-150 0.01-0.1


The contact persons for the infrared beam‐line are Prof. F. Légaré (legare@emt.inrs.ca) and Dr. Heide Ibrahim (ibrahim@emt.inrs.ca).

The LWFA‐based x‐ray beam‐line at the Advanced Laser Light Source (ALLS)

X‐ray source

The measured typical X‐ray source parameters are as follows: 3x109 photons/0:1% bandwidth/sr/shot at 20 keV, a critical energy between 20 and 30 keV, an effective X‐ray source size of 1.5 μm, a divergence that can be controlled between 10 and 50 mrads (FWHM), an X‐ray beam pointing stability and an X‐ray energy stability in the few% rms range. The beamline runs at 2.5Hz with a typical 20μJ energy (giving 50μW) in the 30keV‐ 40keV band. Phase contrast imaging can be realized in the in‐line geometry and a standard transmission geometry with a divergent beam is used. The object to be imaged is positioned between the X‐ray source and the detection system. R1 and R2 were respectively the source to object and the object to detector distances. The magnification M was thus given by M=(R1+R2)/R1. R2 is limited by the laboratory space to a maximum value of 300cm. Many calibrations objects including a series of nylon fibers placed with diameter ranging from 10μm to 400μm are available.

Methodology

The X‐ray source is driven by the 2.5Hz high‐peak power laser system of ALLS: Laser parameters on target can be varied in the range of 80TW and 220TW peak power, with laser energy in the range between 1J and 4J at pulse durations in the range of 18fs to 35fs. The laser beam is focused in a gas jet (nozzle with length varied between 3mm and 10mm) with an off‐axis parabola (1.5m focal length) in a spot (central spot) diameter around 15μm. Laser intensity, IL, on target can be varied between 5x1018W/cm2 and 5x1019W/cm2 giving a field amplitude, a0 between 1.5 and 5. The gas jet electron density, n, can be adjusted between 1018cm‐3 and 1019cm‐3 in order to explore a range of ratio P/Pc between 4 and 80, where Pc is the critical power (Pc = 17 (nc/n) [GW]).

Diagnostics

Diagnostics include phase front & pulse duration for the laser pulse (at full energy), the far‐ field and near field, the optical spectrum, time‐resolved transverse shadowgraphy (15μm and 50fs resolutions), Thomson scattering, electron spectrum (100MeV – 1GeV), and several X‐ray CCD cameras.

Specifications of the high‐peak power laser

Parameter

Value

Center wavelength 800 nm
Pulse duration (FWHM) 22 fs
Max energy on target 4 J
Shot energy stability 1.22% rms
F/number @ target 15
Intensity FWHM @ target 15 μm
Strehl ratio @ target >0.9 with deformable mirror
Energy containment @ target 80% within 1/e2 radius
Pointing stability 5 μrad
Pre‐pulse contrast @ ns scale 8e‐9 @ 10 ps
Pre‐pulse contrast @ ps scale 2.5 Hz

 

The contact persons for the x‐ray beam‐line are Prof. J.C. Kieffer (kieffer@emt.inrs.ca) and Dr. S. Fourmaux (fourmaux@emt.inrs.ca) at INRS‐EMT.

 

François Légaré francois.legare@emt.inrs.ca