Investigation of Pico-second Laser Heating Process of Polymer-Film through Thermo-Modulation Spectroscopy

通过热调制光谱研究聚合物薄膜的皮秒激光加热过程

基本信息

批准号：
08650253
负责人：
HANAMURA Katsunori
金额：
$ 1.6万
依托单位：
Gifu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

Thermo-modulation spectroscopy is applied for the investigation of the relaxation process in nano-seconds laser heating of a polystirene-film. A thin polystirene-film of a 1 micron thickness is pasted on a polished copper surface. The film is heated by a pulse beam of CO_2 laser (wavelength of 10.6 microns) ; where a CW laser beam is modulated by a chopper which is made of a stainless disc of 120 mm diameter and 0.2 mm thickness and is rotated by synchronous motor with 24000 rpm. Since there are180 slits on the circumference of the disc, when the width of the slit is 250 microns, the half-width of the pulse beam is about 2 micro-seconds and the interval of each pulse is 14 micro-seconds. With the cycle, the polystirene-film is heated and cooled, alternately. In relation to the pulse beam of CO_2 laser, the beam of He-Ne laser (wavelength of 3.39 microns) modulated by the same chopper is incident on the same point of the film. The reflected beam intensity of He-Ne laser is measured by P … More bS detector. In this case, the delay time between two pulse beams can be set up arbitrarily. That is, with increasing delay time the time history of the reflectivity of the film for the wavelength of 3.39 microns is obtained after the film is heated by one pulse of CO_2 laser.In experiment, since it is not clear when the two pulse beams are synchronized completely, the delay time is increased from an arbitrary time, i.e., zero second, to the time interval of 14 micro-seconds at an regular intervals of 300 nano-seconds. As a result, at a delay time the reflected beam intensity begins to increase drastically and then decreases sharply with increasing delay time. That is, only for about 2 micro-seconds the reflected beam intensity changes, which may mean that the two pulse beams are synchronized around the time. Consequently, it is disclosed that the thermo-modulation spectroscopy is successfully applied for the investigation of a high speed heating process by an infrared laser, with the time resolution of an order of a few hundred nano-seconds.The frequency of CO_2 laser is close to that of deforming vibration of C=C-H in the benzene nucleus in the polystirene, while the frequency of He-Ne laser is much the same as that of the stretching vibration of -CH_2-. Since the time resolution of the thermo-modulation spectroscopy is close to the relaxation time from a vibrational mode to other vibrational and/or rotational modes (<100 nano-seconds), the relaxation process in nano-seconds laser heating is expected to be captured through the infrared-ray thermo-modulation spectroscopy. Less

热调制光谱用于研究聚苯乙烯薄膜的纳秒激光加热的弛豫过程。将 1 微米厚的薄聚苯乙烯薄膜粘贴在抛光的铜表面上，通过脉冲加热该薄膜。 CO_2激光束（波长10.6微米）；其中CW激光束由直径120毫米、厚度0.2毫米的不锈钢盘制成的斩波器调制。由同步电机以24000rpm旋转，由于圆盘圆周上有180个狭缝，当狭缝宽度为250微米时，脉冲束的半宽度约为2微秒，每个狭缝的间隔约为2微秒。脉冲为14微秒，相对于CO_2激光的脉冲束，聚苯乙烯薄膜被交替加热和冷却。由同一斩波器调制的 He-Ne 激光（波长为 3.39 微米）入射到薄膜的同一点，由 P … 更多 bS 探测器测量 He-Ne 激光的反射光束强度。两脉冲束之间的时间可以任意设置，即随着延迟时间的增加，在CO_2激光的一脉冲加热后，得到薄膜对3.39微米波长的反射率的时间历程。实验中，由于不清楚两个脉冲束何时完全同步，因此将延迟时间从任意时间，即零秒，以300纳秒的固定间隔增加到14微秒的时间间隔。结果，在延迟时间处，反射光束强度开始急剧增加，然后随着延迟时间的增加而急剧减小，即，反射光束强度仅在大约2微秒内发生变化，这可能意味着两个脉冲光束是不同的。测试表明，热调制光谱已成功应用于红外激光高速加热过程的研究，时间分辨率达到数百纳秒量级。 CO_2激光的频率与聚苯乙烯苯核中C=C-H的变形振动频率接近，而He-Ne激光的频率与-CH_2-的伸缩振动频率大致相同。热调制光谱的时间分辨率接近从振动模式到其他振动和/或旋转模式的弛豫时间（<100纳秒），纳秒激光加热的弛豫过程有望通过红外热调制光谱。