LightMachinery

LightMachinery光机公司

光机公司 (LightMachinery Inc.) 是位于加拿大首都渥太华的一家专业生产精密光学元件，光学加工设备和激光系统的公司。擅长于通过对现有加工工艺的改进和提高，生产出精度要求非常严苛的光学产品，以满足用户的特殊需要。

光机公司的工作人员都是光学加工或激光领域的行家里手。几乎每个雇员都具有在光学设计、大功率激光器、精密光学加工、激光系统、表面分析、光学镀膜或机加工等领域中的某个领域的20年以上的工作经验。已经成功地为全球范围内的顾客提供高质量的光学元件和激光设备，应用范围涵盖空间科学、光通讯、半导体、高能激光、科学研究、非破坏性检测、电子、制药以及材料加工等多个领域。

作为一家高科技创新公司，光机公司现位于加拿大国家研究中心 (National Research council of Canada -- NRC)内。主要办公室和实验室位于研究中心的M-50 楼内的“工业合作设施” (Industrial Partnership Facility -- IPF)里，而研发和光学加工则设在M-38 楼的国家测量标准所(Institute for National Measurement Standards)内。通过依托于具有国际水平的科研院所，光机公司在光学加工、光学测量以及光学镀膜等方面得到了加拿大国家研究中心的多方支持，这使得可以把主要精力和研究力量集中到新技术和新工艺的应用上来。

通过利用加拿大国家测量标准所原有的光学加工设备和自己添置的设备，可以在各种光学材料上制备出光学平面、球面、柱面以及其它非球面，精度可以达到 1/100 激光波长的量级。

另一方面，激光应用实验室装备有 GSI Lumonics 的大功率二氧化碳激光器以及准分子激光器。我们在激光应用和激光加工设备的设计等方面的经验使得我们可以在我们的实验室内对工业或科研部门提供的样品进行激光处理，以找到设备配置和激光工作参数。光机公司的技术人员曾经参与过大量的激光应用方面的研发项目，包括：印刷电路板的打孔、啤酒瓶打标、药片打孔、胶囊打标、紫外和红外光谱仪以及激光等离子体超声波的激发等。

Virtually Imaged Phase Arrays - VIPAs

VIPA is the acronym for “Virtually Imaged Phase Array”. A VIPA is a special case of Fabry-Perot etalon with three distinct coatings. This results in quite different performance compared to a regular etalon. One surface of a VIPA has an anti-reflection coated section adjacent to a high reflector. The opposite surface is coated with a partially transmitting mirror. Typically, the partial reflector has a reflectance >90%. Light is introduced into the VIPA at a line focus on the AR coated area. The two surfaces are parallel, and the VIPA is tilted so that the portion reflected from the partial reflector is fully incident on the high reflectance zone of the input surface.

So, a single input beam is converted to a series of parallel output beams of gradually decreasing intensity. These beams will constructively interfere at an angle that depends on the wavelength. Placing a lens between the VIPA and an array detector (CCD or similar) allows recording of a spectrum of the input light. Each subsequent beam has a precise increase in phase and fixed lateral displacement, hence “phase array”.

There are several parameters that define the performance of a VIPA. The first is its optical thickness. For a solid etalon this is OPD=2ntcos(θ), where n is the refractive index, t is the thickness, and θ is the angle from normal within the VIPA. From the optical thickness, the free spectral range (FSR) is approximately c/OPD. Analogous to a regular etalon, the angular dispersion of the VIPA output will repeat every time the input frequency (or wavelength) increases by 1 FSR.

The second important parameter is the reflectance of the output mirror. In principle, a higher reflectance mirror will increase the resolving power of the VIPA. Our experience is that a reflectivity of about 95% will result in a finesse of about 50. In other words, it will be possible to distinguish wavelengths separated by 1/50th of the FSR.

The third important parameter is the internal angle of the light travelling through the VIPA. Smaller angles increase the angular dispersion, but there are a couple of factors that put a lower limit on this angle. The first reflection from the partial reflector must be fully incident on the high reflector so a narrower transition between the antireflection coating and the high reflector enables a smaller angle. This transition is typically less than 100 μm. Secondly, the lateral offset of the reflected beam must be greater than the width of the input beam plus the width of the coating transition. Normally, this condition is optimized when the beam waist is located where the input beam first reflects from the partial reflector.

The VIPA coatings must be selected to match the wavelength range of interest, and the substrate material must also be transparent. The LightMachinery catalog VIPAs are all made of fused silica. Customized designs using calcium fluoride or silicon allow operation further into the infra-red.