Background: The diode laser was utilized in soft tissue incision of oral surgery based on the photothermic effect. The contradiction between the ablation efficiency and the thermal damage has always been in diode laser surgery, due to low absorption of its radiation in the near infrared region by biological tissues. Fiber-optic thermal converters (FOTCs) were used to improve efficiency for diode laser surgery. The purpose of this study was to determine the photothermic effect by the temperature and residual laser energy on film FOTCs.

Methods: The film FOTC was made by a distal end of optical fiber impacting on paper. The external surface of the converter is covered by a film contained amorphous carbon. The diode laser with 810 nm worked at the different rated power of 1.0 W, 1.5 W, 2.0 W, 3.0 W, 4.0 W, 5.0 W, 6.0 W, 7.0 W, 8.0 W in continuous wave (CW)and pulse mode. The temperature of the distal end of optical fiber was recorded and the power of the residual laser energy from the film FOTC was measured synchronously. The temperature, residual power and the output power were analyzed by linear or exponential regression model and Pearson correlations analysis.

Results: The residual power has good linearity versus output power in CW and pulse modes (R² = 0.963, P < 0.01 for both). The temperature on film FOTCs increases exponentially with adjusted R² = 0.959 in continuous wave mode, while in pulsed mode with adjusted R² = 0.934. The temperature was elevated up to about 210 °C and eventually to be a stable state. Film FOTCs centralized approximately 50% of laser energy on the fiber tip both in CW and pulsed mode while limiting the ability of the laser light to interact directly with target tissue.

Conclusions: Film FOTCs can concentrate part of laser energy transferred to heat on distal end of optical fiber, which have the feasibility of improving efficiency and reducing thermal damage of deep tissue.

背景：基于光热效应，二极管激光器被用于口腔外科的软组织切口。消融效率与热损伤之间的矛盾一直存在于二极管激光手术中，这是由于生物组织在近红外区域对辐射的吸收较低。光纤热转换器（FOTC）用于提高二极管激光手术的效率。这项研究的目的是通过温度和残余激光能量确定薄膜FOTC上的光热效应。

方法：薄膜FOTC是由光纤的远端撞击在纸上制成的。转换器的外表面被包含无定形碳的膜覆盖。810 nm的二极管激光器在连续波（CW）和脉冲模式下以1.0 W，1.5 W，2.0 W，3.0 W，4.0 W，5.0 W，6.0 W，7.0 W，8.0 W的不同额定功率工作。记录光纤远端的温度，并同步测量来自薄膜FOTC的剩余激光能量的功率。通过线性或指数回归模型和皮尔逊相关分析来分析温度，剩余功率和输出功率。

结果：在CW和脉冲模式下，相对于输出功率，剩余功率具有良好的线性度（R ²  = 0.963， 两者均P <0.01）。 在连续波模式下，调整后的R ² = 0.959时，薄膜FOTC上的温度呈指数增长，而在调整后的R ²  = 0.934的脉冲模式下，薄膜FOTC的温度呈指数增长。将温度升高至约210℃，并最终达到稳定状态。薄膜FOTC在CW和脉冲模式下将大约50％的激光能量集中在光纤尖端，同时限制了激光与目标组织直接相互作用的能力。

结论：薄膜FOTC可以将传递给热的部分激光能量集中在光纤的远端，具有提高效率和减少深层组织热损伤的可行性。