LE-0600 Diode pumped Nd:YAG Laser

Topics:

  • Properties of Diode laser

  • Optical Pumping

  • Rate Equation Model

  • Static and dynamic laser behavior

  • Output Power

  • Optical Resonator

  • Resonator Stability Criterion

  • Transverse Modes

  • Spiking

  • Hemi Spherical Resonator

  • Spherical Resonator

  • Laser Line Tuning


LE-0600 Diode pumped Nd:YAG Laser, hemi-spherical cavityA. LE-0600 Diode pumped Nd:YAG Laser with hemi-spherical cavity

LE-0600 Diode pumped Nd:YAG Laser with concentric cavityB. LE-0600 Diode pumped Nd:YAG Laser with concentric cavity

Optical pumping in conjunction with Nd:YAG lasers is of particular interest, because these have become widely accepted for industrial use, along with the CO2 laser. The laser-active material which, in the case of the Nd:YAG laser, is excited by optical pumping, consists of Neodymium atoms that are accommodated in a transparent YAG host crystal (Yttrium Aluminum Garnet).
Whereas up to a few years ago Nd:YAG lasers were always excited using discharge lamps, optical pumping with laser diodes is becoming more and more significant. This is because laser diodes are available economically and they emit narrow band light at high optical powers, which matches the energy levels of the Nd:YAG crystal. The advantage over the discharge lamp is that the emission of laser diodes is nearly completely absorbed by the Nd:YAG, whereas the very wide spectral emission of discharge lamps is absorbed to only a small extent only.
The four level system is explained, a theoretical analysis of the Nd:YAG laser is performed, and a rate equation model derived. The steady state solution is presented, and the dynamic situation considered to investigate spiking.
Besides the set-up with a hemi-spherical cavity (Fig. A.), a concentric cavity (Fig. B.) can also be arranged. In this case, the Nd:YAG rod has only an anti-reflection coating and is placed in the center of the cavity.
The kit contains all components necessary to assemble a diode pumped Nd:YAG laser - a 1 W diode (LD) with driver and Peltier controller, collimating (CO) and focusing optics (FL), Nd:YAG crystal (ND), laser mirror (M1), a photodiode detector (PD) with filer (FI) and all necessary mounts etc.
The stability criterion of the resonator are verified experimentally. The dependence of the pump wavelength on diode temperature and drive current are proven, and the absorption spectrum of Nd:YAG derived. By using a few additional modules, this basic set-up can be up-graded to LE-0700 „Frequency Doubling with KTP“ or LE-0800 „Generation of short pulses“. Furthermore the components for the oscillation at 1.3 µm including frequency doubling to "red" or an active or passive Q-switch are available as options.
Energy level diagram of the Nd:YAG LaserEnergy level diagram of the Nd:YAG Laser Laser operation of Neodymium was first demonstrated by J. E. Geusic et al. at Bell Laboratories in 1964. In the same way as for Chromium atoms of the ruby laser the Neodymium atoms are embedded in a host crystal which in this case is a composition of Yttrium, Aluminum and Oxygen (Y3Al5O12) forming a clear crystal of the structure of a garnet. The Neodymium is replacing a small fraction of the Yttrium atoms and due to the integration inside the lattice it is triply ionized (Nd3+). The outstanding property of such a Nd:YAG laser lies in the fact that the laser process takes place inside a 4 level energy system as shown on the left. This and the possibility of creating more than 10.000 W output power made this laser to an indispensable tool for a great variety of applications. Furthermore this laser system is an integral part of the lectures in photonics since it exhibits the important level laser system. In this system the population inversion is created between the energy levels (3) and (4) and since (2) is far above the ground state its population is zero. So even a single excited Neodymium ion provides an population inversion.

Nd:YAG Laser principle with hemi spherical cavityPrinciple of Nd:YAG Laser with hemi spherical cavity

For the excitation of the Neodymium ions a laser diode (LD) is used which emits laser radiation at a wavelength of 808 nm. The collimator (CO) transforms the emission in an almost parallel light bundle which is focused by the lens (FL) into the Nd:YAG rod. To shape the beam to a more round one, a cylinder lens telescope (CL). The optically cavity is formed by the mirror M1 and M2 whereby the plane mirror M1 is coated to ones side of the Nd:YAG rod and the spherical mirror M2 has a radius of 100 mm.

Nd:YAG Laser principle with concentric cavityPrinciple of Nd:YAG Laser with concentric cavity

In this arrangement a Nd:YAG rod is used, which has only an anti reflection coating for the laser wavelength of 1064, 1150 and 1330 nm and for the pump wavelength of 808 nm. The Nd:YAG rod is located in the center between the two spherical mirror each having a radius of curvature of 100 mm.
LE-0600 Diode pumped Nd:YAG Laser, consisting of:
Item Code Qty. Description
1 CA-0060 1 Infrared display card 0.8 -1.4 µm
2 CA-0080 1 Optics cleaning set
3 CA-0450 3 BNC connection cable 1 m
4 DC-0040 1 Diode laser controller MK1
5 DC-0120 1 Si-PIN Photodetector, BPX61
6 MM-0020 3 Mounting plate C25 on carrier MG20
7 MM-0060 1 Filter plate holder on MG20
8 MM-0090 1 XY adjuster on MG20
9 MM-0100 1 Target Cross in C25 Mount
10 MM-0462 1 Kinematic mirror mount M16, right
11 MP-0150 1 Optical Bench MG-65, 500 mm
12 OC-0060 1 Biconvex lens f=60 mm in C25 mount
13 OC-0170 1 Collimator 808 nm in C25 mount
14 OC-0950 1 Filter RG1000 50x50x3 mm
15 OC-1070 1 Laser mirror M16, ROC 100 mm, HR @ 1064 nm
16 OM-0052 1 Cylindrical Beam Expander 3x
17 OM-0624 1 Nd:YAG rod in 2 axes kinematic mount
18 OM-L520 1 Diode laser module 808 nm 1W
19 UM-LE06 1 Manual for Nd:YAG Laser
Required Option (order separately)
20 CA-0200 1 Oscilloscope 100 MHz digital, two channel
Option (order separately)
21 CA-0260 1 Laser power meter LabMax-TO
22 CA-0266 1 Power sensor PM3 0.5 mW to 2W
23 CA-0270 1 Fibre coupled spectrometer 200 - 1200 nm, USB
24 LE-0620 1 Concentric Cavity Extension
25 LE-0710 1 "Green" 532 nm SHG extension
26 LE-0720 1 "Red 660 nm" SHG Extension
27 LE-0810 1 Passive Q-Switch Extension
28 LE-0820 1 Active Q-switch Extension
29 OC-1060 1 Laser mirror M16, ROC 100 mm, T 2% @ 1064 nm
30 OM-0580 1 Birefringent Tuner
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