LCS, Inc. represents
Laser Crystal Solutions project
Stage I: Industrial Crystal Growth: Laser host material KGW and KYW

>> back to start page >>

Direct shortcuts to our products

Nonlinear Crystal products:

LBO nonlinear crystals
Lithium Triborate
Chemical formula: LiB3O5
BBO nonlinear crystals
beta-Barium Borate
Chemical formula: BaB2O4
BBO e-o switches
KTP nonlinear crystals
Potassium Tytanil Phosphate
Chemical formula: KTiOPO4
KGW, KYW laser host material
Raman Shifters (KGW, KYW)
Optical Coatings
anti-reflection and protective

Laser products:

Optical Parametric Oscillator

Contact information:

Zelenaja gorka str. 1,
630060, Novosibirsk,
Russian Federation
Phone/Fax: +7 (383) 334 80 81

e-mail: sales@lc-solutions.com

This page is dedicated to Yb-doped KGW and KYW. Read about Nd-doped KGW - here -.

Potassium Gadolinium Tungstate KGd[WO4]2 (KGW)
and
Potassium Yttrium Tungstate KY[WO4]2 (KYW)

Standard Specifications
Available Optical Coatings

Description

Applications

Yb3+ doped Potassium Tungstate materials are attractive as efficient active media because they possess several important advantages over the widely used Nd3+ doped materials:
- the broad spectral emission band of Yb:KYW allows the tuning of the laser radiation over 1020-1060 nm range and the generation of pulses as short as 90 fs;
- enhanced storage capacity, wide absorption spectrum at 980 nm and high absorption of pump radiation in a small crystal region allow an efficient use of diode laser pump;
- the small quantum defect enhances the overall efficiency and reduces the thermal load;
- three to four times longer emission lifetime, increasing the energy-storage time;
- roughly three times smaller Stokes shift between absorption and emission (laser quantum defect), reducing the thermal load;
- an extremely simple two-level electronic structure, eliminating the possibility for unwanted competitive processes as excited-state absorption and upconversion;
- laser efficiency is not degraded by concentration quenching and very high doping level is possible which can considerably reduce the requirements to the beam quality of the laser diodes used for pumping.
Yb-doped materials are characterized by a large third order non-linear optical susceptibility, being efficient Raman converters for ps/ns laser pulses.
As compared to YAG or glasses used as hosts for Yb3+, KYW and KGdW have the advantage of a larger absorption cross section than YAG, which decreases the minimum pump intensity necessary to achieve transparency in the quasi-two-level system of ytterbium.
On the other hand, a disadvantage of Yb-doped laser materials is their quasi-three-level nature. As a result, they reabsorb a part of the emitted laser light. To saturate this loss mechanism high pump intensity and a good overlap of pump and resonator mode over the whole length of the laser medium are required.

Parameter

KGW

KYW

Crystal Strusture

monoclinic

monoclinic

Space Group

C62h-C2/c

C62h-C2/c

Cell Parameters

a = 0.809 nm
b = 1.043 nm
c = 0.7588 nm
b = 94°

a = 0.805 nm
b = 1.035 nm
c = 0.754 nm
b = 94°

Spectroscopic Properties

Parameter

3% Nd:KGW 5% Yb:KYW 5% Yb:KGW
Absorption peak wavelength, lpump, [nm] 810 981.2 981.2
Absorption linewidth, Dlpump, [nm] 4.5 3.5 3.7
Peak absorption cross-section, spump, [cm2] 1.19x10-19 1.33x10-19 1.2x10-19
Peak absorption coefficient, [cm-1] 20 40 26
Emission wavelength, lse, [nm] 1067 1025 1023
Emission linewidth, Dlse, [nm] 24 16 20
Peak emission cross-section, sse, [cm2] 4.3x10-19 3x10-20 2.8x10-20
Quantum effect, lpump/lse, [nm] 0.759 0.957 0.959
Fluorescence lifetime, tem, [ms] 0.1 0.6 0.6

Possible dopant concentrations

Yb:KYW

Yb:KGW

1 - 10 at. %

1 - 5 at. %

Yb-doped laser materials are well suited for building simple and robust diode-pumped femtosecond lasers delivering output powers in the Watt range.
The ytterbium containing active media are attractive for application in all solid-state diode pumped lasers emitting at about 1 microm because of their favourable spectroscopic properties leading to small quantum gap and therefore to low thermal loading. InGaAs laser diodes can be used for pumping such lasers between 0.9 and 1.0 mm.
Another feature of Yb lasers is the possibility of broadband laser generation and therefore of building tunable or ultrashort pulse laser systems.

CW and Q-switched laser operation of LD pumped Yb-doped potassium yttrium tungstate with ytterbium concentration of 5% is used for tunable and ultra-short pulse laser systems with low average output power.
Diode pumping of KYW:Yb and KGdW:Yb has been demonstrated between 965 and 980 nm. Their emission cross section is larger than in YAG or in glasses and the thermal conductivity has an intermediate position (it is four times better than in glasses). The laser quantum defect is less than in YAG.

The emission linewidth of KYW:Yb or KGdW:Yb is broader than in YAG and comparable to that in glasses. This linewidth is interesting not only for potential tuning but mainly for the generation and amplification of short (ps or fs) laser pulses.
Mode-locking of a diode-pumped KGdW:Yb laser has been demonstrated and utilization of the crystal anisotropy for maximum gain bandwidth culminated in the generation of 71 fs pulses with KYW:Yb in 2001.
Also, the first regenerative amplification of fs pulses in KYW:Yb has been demonstrated in 2001. Whereas fs pulses can provide ultimate peak powers, much higher average powers and optimum conditions for frequency conversion to other wavelengths can be realized with slightly longer pulses (1 ps or more for Raman conversion).
The slope efficiency up to 78% was demonstrated with the Ti:Sapphire-laser and 66% with the diode laser pumping. This high value of the slope efficiency opens potential for further nonlinear optical conversion of this radiation with a good overall efficiency.

Please, contact us for any specific requirements.

Powered by: LCS, Inc. © 2006