LightMachinery光機公司

光機公司 (LightMachinery Inc.) 是位于加拿大首都渥太華的一家專業生產精密光學元件，光學加工設備和激光系統的公司。擅長于通過對現有加工工藝的改進和提高，生產出精度要求非常嚴苛的光學產品，以滿足用戶的特殊需要。

光機公司的工作人員都是光學加工或激光領域的行家里手。幾乎每個雇員都具有在光學設計、大功率激光器、精密光學加工、激光系統、表面分析、光學鍍膜或機加工等領域中的某個領域的20年以上的工作經驗。已經成功地為全球范圍內的顧客提供高質量的光學元件和激光設備，應用范圍涵蓋空間科學、光通訊、半導體、高能激光、科學研究、非破壞性檢測、電子、制藥以及材料加工等多個領域。

作為一家高科技創新公司，光機公司現位于加拿大國家研究中心 (National Research council of Canada -- NRC)內。主要辦公室和實驗室位于研究中心的M-50 樓內的“工業合作設施” (Industrial Partnership Facility -- IPF)里，而研發和光學加工則設在M-38 樓的國家測量標準所(Institute for National Measurement Standards)內。通過依托于具有國際水平的科研院所，光機公司在光學加工、光學測量以及光學鍍膜等方面得到了加拿大國家研究中心的多方支持，這使得可以把主要精力和研究力量集中到新技術和新工藝的應用上來。

通過利用加拿大國家測量標準所原有的光學加工設備和自己添置的設備，可以在各種光學材料上制備出光學平面、球面、柱面以及其它非球面，精度可以達到 1/100 激光波長的量級。

另一方面，激光應用實驗室裝備有 GSI Lumonics 的大功率二氧化碳激光器以及準分子激光器。我們在激光應用和激光加工設備的設計等方面的經驗使得我們可以在我們的實驗室內對工業或科研部門提供的樣品進行激光處理，以找到設備配置和激光工作參數。光機公司的技術人員曾經參與過大量的激光應用方面的研發項目，包括：印刷電路板的打孔、啤酒瓶打標、藥片打孔、膠囊打標、紫外和紅外光譜儀以及激光等離子體超聲波的激發等。

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.