News - Why we are using Nd: YAG crystal as the gain medium in DPSS laser?

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What is a Laser Gain Medium?

A laser gain medium is a material that amplifies light by stimulated emission. When the medium's atoms or molecules are excited to higher energy levels, they can emit photons of a particular wavelength when returning to a lower energy state. This process amplifies the light passing through the medium, which is fundamental to laser operation.

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What’s the Usual Gain Medium?

The gain medium can be varied, including gases, liquids (dyes), solids (crystals or glasses doped with rare-earth or transition metal ions), and semiconductors. Solid-state lasers, for example, often use crystals like Nd: YAG (Neodymium-doped Yttrium Aluminum Garnet) or glasses doped with rare-earth elements. Dye lasers use organic dyes dissolved in solvents, and gas lasers utilize gases or gas mixtures.

Laser rods (from left to right): Ruby, Alexandrite, Er:YAG, Nd:YAG

The differences between Nd (Neodymium), Er (Erbium), and Yb (Ytterbium) as gain mediums

primarily relate to their emission wavelengths, energy transfer mechanisms, and applications, especially in the context of doped laser materials.

Emission Wavelengths:

- Er: Erbium typically emits at 1.55 µm, which is in the eye-safe region and highly useful for telecommunications applications due to its low loss in optical fibers (Gong et al., 2016).

- Yb: Ytterbium often emits around 1.0 to 1.1 µm, making it suitable for a wide range of applications, including high-power lasers and amplifiers. Yb is often used as a sensitizer for Er to enhance the efficiency of Er-doped devices by transferring energy from Yb to Er.

- Nd: Neodymium-doped materials typically emit around 1.06 µm. Nd:YAG, for example, is renowned for its efficiency and is widely used in both industrial and medical lasers (Y. Chang et al., 2009).

Energy Transfer Mechanisms:

- Er and Yb Co-doping: The co-doping of Er and Yb in a host medium is beneficial for enhancing the emission in the 1.5-1.6 µm range. Yb acts as an efficient sensitizer for Er by absorbing pump light and transferring energy to Er ions, leading to amplified emission in the telecommunications band. This energy transfer is crucial for the operation of Er-doped fiber amplifiers (EDFA) (D. K. Vysokikh et al., 2023).

- Nd: Nd does not typically require a sensitizer like Yb in Er-doped systems. Nd's efficiency is derived from its direct absorption of pump light and subsequent emission, making it a straightforward and efficient laser gain medium.

Applications:

- Er: Primarily used in telecommunications due to its emission at 1.55 µm, which coincides with the minimum loss window of silica optical fibers. Er-doped gain mediums are critical for optical amplifiers and lasers in long-distance fiber optic communication systems.

- Yb: Often used in high-power applications due to its relatively simple electronic structure that allows for efficient diode pumping and high power output. Yb-doped materials are also used to enhance the performance of Er-doped systems.

- Nd: Well-suited for a wide range of applications, from industrial cutting and welding to medical lasers. Nd:YAG lasers are particularly valued for their efficiency, power, and versatility.

Why did we choose Nd:YAG as the gain medium in DPSS laser

A DPSS laser is a type of laser that uses a solid-state gain medium (like Nd: YAG) pumped by a semiconductor laser diode. This technology allows for compact, efficient lasers capable of producing high-quality beams in the visible-to-infrared spectrum. For a detailed article, you might consider searching through reputable scientific databases or publishers for comprehensive reviews on DPSS laser technology.

[Related Product : Diode-pumped solid-state laser]

Nd:YAG is often used as a gain medium in semiconductor-pumped laser modules for several reasons, as highlighted by various studies:

1.High Efficiency and Power Output: A design and simulations of a diode side-pumped Nd:YAG laser module demonstrated significant efficiency, with a diode side-pumped Nd:YAG laser providing a maximum average power of 220 W while maintaining constant energy per pulse in a wide frequency range. This indicates the high efficiency and potential for high power output of Nd:YAG lasers when pumped by diodes (Lera et al., 2016).
2.Operational Flexibility and Reliability: Nd:YAG ceramics have been shown to operate efficiently at various wavelengths, including eye-safe wavelengths, with high optical-to-optical efficiency. This demonstrates Nd:YAG's versatility and reliability as a gain medium in different laser applications (Zhang et al., 2013).
3.Longevity and Beam Quality: Research on a highly efficient, diode-pumped, Nd:YAG laser emphasized its longevity and consistent performance, indicating Nd:YAG's suitability for applications requiring durable and reliable laser sources. The study reported extended operation with more than 4.8 x 10^9 shots without optical damage, maintaining excellent beam quality (Coyle et al., 2004).
4.Highly Efficient Continuous-Wave Operation: Studies have demonstrated the highly efficient continuous-wave (CW) operation of Nd:YAG lasers, highlighting their effectiveness as a gain medium in diode-pumped laser systems. This includes achieving high optical conversion efficiencies and slope efficiencies, further attesting to the suitability of Nd:YAG for high-efficiency laser applications (Zhu et al., 2013).

The combination of high efficiency, power output, operational flexibility, reliability, longevity, and excellent beam quality makes Nd:YAG a preferred gain medium in semiconductor-pumped laser modules for a wide range of applications.

Reference

Chang, Y., Su, K., Chang, H., & Chen, Y. (2009). Compact efficient Q-switched eye-safe laser at 1525 nm with a double-end diffusion-bonded Nd:YVO4 crystal as a self-Raman medium. Optics Express, 17(6), 4330-4335.

Gong, G., Chen, Y., Lin, Y., Huang, J., Gong, X., Luo, Z., & Huang, Y. (2016). Growth and spectroscopic properties of Er:Yb:KGd(PO3)_4 crystal as a promising 155 µm laser gain medium. Optical Materials Express, 6, 3518-3526.

Vysokikh, D. K., Bazakutsa, A., Dorofeenko, A. V., & Butov, O. (2023). Experiment-based model of Er/Yb gain medium for fiber amplifiers and lasers. Journal of the Optical Society of America B.

Lera, R., Valle-Brozas, F., Torres-Peiró, S., Ruiz-de-la-Cruz, A., Galán, M., Bellido, P., Seimetz, M., Benlloch, J., & Roso, L. (2016). Simulations of the gain profile and performance of a diode side-pumped QCW Nd:YAG laser. Applied Optics, 55(33), 9573-9576.

Zhang, H., Chen, X., Wang, Q., Zhang, X., Chang, J., Gao, L., Shen, H., Cong, Z., Liu, Z., Tao, X., & Li, P. (2013). High efficiency Nd:YAG ceramic eye-safe laser operating at 1442.8 nm. Optics Letters, 38(16), 3075-3077.

Coyle, D. B., Kay, R., Stysley, P., & Poulios, D. (2004). Efficient, reliable, long-lifetime, diode-pumped Nd:YAG laser for space-based vegetation topographical altimetry. Applied Optics, 43(27), 5236-5242.

Zhu, H. Y., Xu, C. W., Zhang, J., Tang, D., Luo, D., & Duan, Y. (2013). Highly efficient continuous-wave Nd:YAG ceramic lasers at 946 nm. Laser Physics Letters, 10.

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