Ultimate Control in Semiconductor Lasers

目前半导体激光器的应用范围很广，渗透到生活的方方面面。事实上，在发达国家，大多数人已经拥有了几台激光器，并从更多的激光器中获益。随着每一项新技术的出现，这种扩散必将继续下去。最重要的是，激光开启了互联网时代，因为在全球范围内传输的所有数据都是以激光的形式传输的。因此，发达国家的大多数人在一天中都依赖于许多激光。因此，降低它们的拥有成本对于把这些好处扩大到发展中世界并给我们大家带来新的好处是至关重要的。随着新技术和新应用的不断涌现，光子学未来的潜在应用似乎是无限的。半导体激光器的主要优点是，如果应用程序有足够大的体积，半导体激光器的成本非常低。DVD播放机就是一个很好的例子——激光每台只花几便士。因此，半导体激光器使新技术、新设备和新工艺得以商业化。然而，半导体激光器必须能够产生所需的光的“味道”；即正确的波长，光谱宽度，功率，偏振，光束形状等。半导体激光器的一些基本参数可以通过设计和材料的选择来控制，例如波长，光谱纯度（线宽）。然而，使用目前的技术，偏振和光束轮廓通常是在制造时固定的，并且可能仅在随后由外部光学元件改变。这会带来额外的成本（增加对环境的影响），并降低设备的整体效率和实用性。对于未来的工程师和科学家来说，完全控制半导体激光器的输出将是理想的，这将为未来的应用提供无限的可能性。已知物质在光波长尺度上的变化允许控制材料的光学性质。即使是像鼠标这样简单的东西中的激光也包含了许多这样的技术。我们将开发新的纳米级半导体制造，以改变光与物质的相互作用，并设计控制偏振和激光束的形式。我们的工作将首次实现可量产的光子晶体表面发射激光器（PCSEL）。纳米级光子晶体负责控制激光器的性能。它只是一个与光本身大小相似的周期性图案，这种周期性图案的一个自然例子产生了一些蝴蝶翅膀的蓝色，或者蛋白石的彩虹色。在我们的案例中，光子晶体的每一个细节都将被建模、理解和优化，以控制激光的特性，以满足一系列的需求。激光器将被设计成几乎为零发散，并且还将首次允许电子控制发散和偏振，并允许直接创建定制工程光束轮廓和模式。实现具有理想光束轮廓的高效率、面积可扩展的高功率激光器将有助于降低激光设备制造中的能耗，并降低其拥有成本。所开发的技术将允许对未来光源的最终设计控制，希望将激光应用限制在想象中。一旦成功，这种设备将取代现有的商业光子学中的激光器，并使更多的新兴应用领域成为可能。这将通过向激光设备引入新功能和降低现有产品的成本而成为可能。我们将与物理理解和设备工程一起开发这项技术，并与此类设备的批量制造商的世界领导者密切联系。

Current applications for semiconductor lasers are wide ranging and pervade every aspect of life. Indeed, in the developed world, most people already own several lasers and gain the benefit of many more. With every new technology, this proliferation is set to continue. Most importantly, the laser enables the internet age since all data transmitted around the globe is carried as flashes of laser light. As a consequence most people in the developed world have come to depend on many lasers during a typical day. The reduction in their cost of ownership is therefore of critical importance to the extension of these benefits to the developing world and also bringing new benefits to us all.The potential future applications of photonics are seemingly unlimited, with new technologies and applications continuing to emerge. The key advantage of a semiconductor laser is that if an application has sufficiently large volume, the cost of the semiconductor laser is very low. The DVD player is a good example -with the laser costing a few pence each. The semiconductor laser therefore enables new technologies, devices and processes to be commercialized. However, semiconductor lasers must be able to generate the required "flavour" of light; i.e. the correct wavelength, spectral width, power, polarization, beam shape, etc.Some of the fundamental parameters of a semiconductor laser may be controlled by the design and choice of materials, e.g. wavelength, spectral purity (line-width). However, using current technologies the polarization and beam profile are generally fixed at manufacture and may only be subsequently altered by extrinsic optical components. This introduces additional cost (increasing the environmental impact) and reduces the overall efficiency and usefulness of the device. For future engineers and scientists it would be ideal if there were complete control of the output from a semiconductor laser, providing unlimited possibilities in terms of future applications. The alteration of matter on the scale of the wavelength of light is known to allow the control of the optical properties of a material. Even the laser in something as simple as a mouse incorporates a number of such technologies. We will develop novel nano-scale semiconductor fabrication to modify light-matter interaction and engineer the control of the polarization and form of a laser beam. Our work will realise a volume manufacturable photonic crystal surface emitting laser (PCSEL) for the first time. The nano-scale photonic crystal is responsible for controlling the properties of the laser. It is simply a periodic pattern similar in size to the light itself, a natural example of this periodic patterning produces the blue colour in some butterfly wings, or the iridescence of opal. In our case, every detail of the photonic crystal will be modeled, understood and optimized to control the properties of the laser to meet a range of needs. Lasers will be designed to exhibit almost zero divergence and will also allow, for the first time, the electronic control of divergence and polarization and allow the direct creation of custom engineered beam profiles and patterns. The realization of high efficiency, area scalable high power lasers with ideal beam profiles will contribute to reduced energy consumption in the manufacture of laser devices, and in their cost of ownership. The technologies developed will allow the ultimate in design control of future optical sources, hopefully limiting laser applications only to the imagination. Once successful, such devices will displace existing lasers in established commercial photonics and enable many more emerging application areas. This will be made possible by introducing both new functionality to laser devices and reducing the cost of existing products. We will develop this technology alongside physical understanding and device engineering, liaising closely with world-leaders in the volume manufacturer of such devices.