1. Picking the laser ion and matrix for lasing
Rare–earth ions
Have shielded electron shells
- Long life times – store energy
Many hosts:
YAG, YLF, YVO4, glass ...
Double tungstates: (KYW )
high rare–earth doping
high cross sections
short crystals can be used
suited for diode pumping

2. Passively Q-switched micro-chiplaser
gunnars laser
Typical data
1 kW, 5 ns, 10 kHz
G. Karlsson, et al., Appl. Opt. 39, 6188 (2000).

3. Diode pumped solid-state laser – the green pointer incorporating nonlinear optics

4. Combination of rare-earth materials and
Engineered nonlinear crystals in DPSSL
Pump diode
Gain media
PPKTP
Frequency Mixing of two DPSSLs in PPKTP
Energy diagram for
Neodymium
Pump
green =
blue =
Turquoise 491=
yellow =
Wavelength Transition Stimulated emission cross-section
1064 nm R2  Y3 4 ·10-19 cm2
946 nm R1  Z ·10-20 cm2
938.5 nm R2  Z ·10-20 cm2

5. Kr-ion laser replacement
Diode pumped Solid-state Lasers - DPSSL
Intra-cavity SFG laser
Yellow light nm -> 593 nm
3 W +3 W gives 700 mW CW yellow light
J. Janousek, S. Johansson, P. Tidemand-Lichtenberg, J. Mortensen, P. Buchhave and F. Laurell, Opt. Exp. 13, (2005).

6. Combined diode and solid-state lasers for Ar-ion laser replacement
An intra-cavity SFG laser locked by a transmission grating
Turqoise laser nm nm
30 mW with modulation
for bio-application
S. Johansson, S. Wang, V. Pasiskevicius, and F. Laurell, Opt. Exp., 13, (2005).

7. Moulded version (plastic)
The Silicon micro-bench laser concept
Laser crystal
Lens
Fiber
Pump
A silicon chip structured
by KOH etching with
sub-micron resolution
Si-chip
Laser-chip mounted
in Si-micro bench
6.5 W at 1064 nm
2 W Q-switched at 1064 nm
with 1.4 ns pulses
Nd:YVO4 chip cut
from a 1 inch wafer
for the Si-chip
Moulded version (plastic)
Q-switch bonded chip
D. Evekull, S. Johansson, S. Bjurshagen, M. Olson, R. Koch and F. Laurell, Electron. Lett, 39, (2004).

8. Er:micro-chip laser tunable with fiber-Bragg grating
Acetylene
G. Karlsson, N. Myrén, W. Margulis, S. Tacheo and F. Laurell, Appl. Opt.. 42, 4327, (2003)

9. Volume Bragg gratings
A grating permanently inscribed in a photothermal glass
Narrowband reflection peak
Tailored performance
Made in durable and cheap glass
Optical
Material
Period, L
Thickness, d
Strength, n1
O.Efimov et al., Appl. Opt. 38, 619, (1999)

10. Why VBGs in lasers ? Reduced linewidth Stabilized output Tunability
Spatial mode filtering
Low quantum defect
Increased efficiency?
The glass
Transparent: nm
High damage treshold: >10 J/cm2, >100kW/cm2
Low absorption: < 0.2%/cm
Low scattering: < 2%/cm

11. External cavity Bulk Bragg grating locked Er-Yb laser
Modes in internal cavity
and external cavity
Frequency tuning
Linewidth < 90 kHz

12. Nd:GdVO4 laser Bandwidth < 40 MHz
B. Jacobsson, et al. “Single-longitudinal-mode Nd-laser with a Bragg-grating Fabry-Perot cavity”, Opt. Express 14, 9284, (2006).

13. Yb:KYW laser with low quantum defect
3 mm, 5% Yb:KYW
Conventional input coupler
Bragg grating input coupler

14. Laser with low quantum defect
Quantum defect: (1.6%) energy difference between pump and laser photons
Motivation
Reduced heat load ->
improved performance at high power
Access to new laser wavelengths (near pump wavelength)
Spatial
Pump: M2 = 35×5
Laser: M2 < 1.1
997 nm
Pump: Dl = 2 nm
Laser: Dl = nm (10GHz)
J. Hellström, B. Jacobsson, V. Pasiskevicius & F. Laurell Opt. Express, 15, (2007)

15. Oblique incidence – change of grating period = wavelength tuning
Beam steering when tuning
No beam steering with retroreflector
Grating at oblique incidence - rotate
l=l0cosq

16. Widely tunable narrow linewidth Yb:KYW laser using volume Bragg gratings
incidence angle
wavelength
Reflectivity 0°
retroreflector
Δλ = nm (10GHz)
Very low quantum (1.6%) defect laser
J. E. Hellström, IEEE J. Quantum Electron, 44, 81 (2008)

17. Why fiber lasers? Fibers guide light efficiently with low losses
Double-clad fibers allows simple poor-pump-to-good-signal conversion, even at high power
Fibers can provide functionality for mode filtering, spectral filtering etc
Fibers have excellent thermal handling
Fiber lasers support a broad gain
Poor quality
pump light

18. Spectral control of fiber lasers
Fiber Bragg gratings (FBGs)
Gain fiber
Difficult to write gratings in doped fibers
Low-loss splicing problematic
Narrow bandwidth
can be a problem
Diffraction gratings
Large beam necessary
for narrow linewidth
Large complicated setups
often necessary

19. VBG locked fiber lasers
Nd-doped fiber - µ-structured design
Core diameter = 18 µm, V-number ~18 (multimode)
Similar slope efficiencies – mirrors vs. VBG
Linewidth 0.07 nm (compared to 7 nm with mirror)
Close to diffraction limited output
Simple cavity design
P. Jelger and F. Laurell, Opt. Express 15, , (2007)

20. High power VBG Er:Yb-fiber laser
Slope eff. ~44 %
Slope eff. ~24 %
Slope eff. ~27 %
Δλ = 0.4 nm
M2~5.5
The role-off at 100 W is due to onset of strong ASE
J. Kim, P. Jelger, J. Sahu, F. Laurell & W. Clarkson, Opt. Letts. 33, 1204 (2008)