Enhanced thermal conductivity of distributed face-cooled composite laser medium included thermal resistance at the bonding interface

Area of Science:

• Materials Science
• Optics and Photonics
• Thermal Engineering

Background:

• Laser gain media require efficient heat dissipation to maintain performance.
• Composite structures offer potential for improved thermal management.
• Interfacial thermal resistance is a critical factor limiting heat transfer in composites.

Purpose of the Study:

• To propose and evaluate a new concept for effective thermal conductivity (κ_eff) in laser gain media using distributed face-cooled composites.
• To investigate the impact of inter-layer surface activated bonding (il-SAB) on interfacial thermal resistance (R) between Nd:YAG and sapphire.
• To compare the κ_eff of composites fabricated using il-SAB, indium foil insertion, and simple contact.

Main Methods:

• Synthesis of Nd:YAG/sapphire composites using inter-layer surface activated bonding (il-SAB).
• Experimental measurement of interfacial thermal resistance (R) at various bonding conditions.
• Calculation of effective thermal conductivity (κ_eff) for different composite configurations.

Main Results:

• il-SAB resulted in negligibly small interfacial thermal resistance (R) between Nd:YAG and sapphire.
• Indium foil insertion and simple contact exhibited significantly higher R values (1.4 × 10⁻⁵ and 4.3 × 10⁻⁴ m²K/W, respectively).
• Composites fabricated by il-SAB achieved the highest κ_eff (15.3 W/mK), compared to 13.9 W/mK (indium foil) and 3.65 W/mK (simple contact).

Conclusions:

• il-SAB is a highly effective method for creating low-resistance interfaces in Nd:YAG/sapphire composites.
• The negligible R achieved with il-SAB enables significant improvement in the κ_eff of laser gain media.
• Optimized composite designs with thicker sapphire components could potentially increase Nd:YAG κ_eff to over 30 W/mK.