Gallium nitride (GaN) and related alloys are important semiconductor materials for fabricating novel photonic devices such as ultraviolet (UV) light-emitting diodes (LEDs) and vertical cavity surface-emitting lasers (VCSELs). Recent technical advances have made free-standing GaN substrates available and affordable. However, these materials are strongly resistant to wet chemical etching and also, low etch rates restrict the use of dry etching. Thus, to develop alternative high-resolution processing for these materials is increasingly important. In this paper, we report the fabrication of microstructures in free-standing GaN using pulsed UV lasers. An effective method was first developed to remove the re-deposited materials due to the laser machining. In order to achieve controllable machining and high resolution in GaN, machining parameters were carefully optimised. Under the optimised conditions, precision features such as holes (through holes, blind or tapered holes) on a tens of micrometer length scale have been machined. To fabricate micro-trenches in GaN with vertical sidewalls and a flat bottom, different process strategies of laser machining were tested and optimised. Using this technique, we have successfully fabricated high-quality micro-trenches in free-standing GaN with various widths and depths. The approach combining UV laser micromachining and other processes is also discussed. Our results demonstrate that the pulsed UV laser is a powerful tool for fabricating precision microstructures and devices in gallium nitride.

Laser scribing of light emitting diode (LED) components on sapphire substrates is shown in this paper to be a viable method of device separation. Three key measurements revealing the effects of UV laser scribing on the LED component performance are discussed and compared for laser scribing at 255 and 355nm. The differences in these two UV wavelengths are further discussed in terms of quality; comparing pulse energies and pulse repetition frequencies for UV ablation of sapphire. In general, these results prove laser processing can be used as an effective high volume manufacturing procedure for substrate separation.

Gallium nitride (GaN) and sapphire are important materials for fabricating photonic devices such as high brightness light emitting diodes (LEDs). These materials are strongly resistant to wet chemical etching and also, low etch rates restrict the use of dry etching. Thus, to develop alternative high resolution processing and machining techniques for these materials is important in fabricating novel photonic devices. In this work, a repetitively pulsed UV copper vapour laser (255 nm) has been used to machine and dice sapphire, GaN and micro LED devices. Machining parameters were optimised so as to achieve controllable machining and high resolution. For sapphire, well-defined grooves 30 μm wide and 430 μm deep were machined. For GaN, precision features such as holes on a tens of micron length scale have been fabricated. By using this technique, compact micro LED chips with a die spacing 100 and a 430 μm thick sapphire substrate have been successfully diced. Measurements show that the performances of LED devices are not influenced by the UV laser machining. Our results demonstrate that the pulsed UV copper vapour laser is a powerful tool for micromachining and dicing of photonic materials and devices.

Lasers are an important tool in the fabrication of photonic components and in particular their use in scribing for separating LED dies on sapphire substrates. This paper describes scribing and cutting of sapphire and GaN using UV lasers (355nm and 266nm harmonics of Nd:YVO4 and 255nm harmonic of CVL). Scribing of sapphire at speeds of 30mm/s have been achieved and cutting of sapphire of up to 700 microns thickness has been demonstrated.

Materials processing using copper vapor lasers is discussed with particular reference to the manufacture of photonics components. The visible and UV wavelengths available from the copper laser can both be used for efficient micromachining of inherently hard materials, such as ceramic, diamond and metal, as well as in the fabrication of fiber Bragg gratings.

UV laser processing of photonic components is discussed with particular reference to components for DWDM (dense wavelength division multiplexing) applications. The photosensitivitiy of generic and specialist optical fibre is compared for UV wavelengths of 255, 271 and 298nm. Materials processing of glass and sapphire at 255nm and the preparation of optical fibres using a laser at 289nm is also presented thereby illustrating the versatility of a multiple UV wavelength source for manufacture of photonics components.UV laser processing of photonic components is discussed with particular reference to components for DWDM (dense wavelength division multiplexing) applications. The photosensitivitiy of generic and specialist optical fibre is compared for UV wavelengths of 255, 271 and 298nm. Materials processing of glass and sapphire at 255nm and the preparation of optical fibres using a laser at 289nm is also presented thereby illustrating the versatility of a multiple UV wavelength source for manufacture of photonics components.

Fiber bragg gratings (FBG) are manufactured by inducing a periodic refractive index change and are used for DWDM, gain flattening and frequency locking telecoms components. The frequency doubled copper vapor laser is a high power deep-UV (255nm) source capable of efficiently inducing the required photorefractive index change for the manufacture of FGBs.The writing of FBGs with the frequency doubled copper vapor laser has been demonstrated in a wide range of optical fiber materials, with high growth rates and high reflectivity gratings. Growth rates as high as 60 dB in 2 seconds have been seen in boron/germanium/hydrogen doped silica fibers and typical growth rates for hydrogen doped standard telecom fiber of 10 dB in 3 0 seconds.The high average power (up to 1000 mW), high repetition rate (6 kHz), low pulse energy (<0.2 mJ) and long coherence length (40 mm), of the UV copper vapor laser make it highly suited to the manufacture of a range of photonics components. These include the production of Bragg gratings in both optical fibers and planar waveguides and the trimming of optical circuits. This paper will report typical growth rates and grating profiles that can be achieved using this source.

Sn-doped silica optical fibres are temperature resistant, have high photosensitivity and low loss at 1.55 µm, properties which make them desirable for use in telecom components and sensors. Results of the fabrication of Bragg gratings in Sn-doped fibres using KrF excimer and UV copper vapour lasers will be presented. 1. Introduction Since the first observation in 1978 by Hill and co-workers [l], photosensitivity has launched many new fields in telecom and fibre optic based devices. In the last decade many papers have been published showing enormous progress both in grating writing techniques and fibre fabrication. New materials have been studied to increase the photosensitivity of telecom optical fibres that would otherwise be insufficient for many applications. SnO2-doping was proposed as a convenient co-dopant [2,3,4,5] because of its low-absorption in the third telecom window at 1.55 µm and high photosensitivity when exposed to 248 KrF excimer laser (KEL) radiation. Recently it was demonstrated that the reflectivity of gratings written with frequency-doubled copper vapour laser (CVL) is similar to the reflectivity of the gratings written with the frequency-doubled argon ion laser [6] . Moreover, the CVL can be used to write simultaneous multiple gratings with identical reflectivity [6,7]. In this work we study the photosensitivity of tin-doped fibres with the CVL and compare it to the photosensitivity achieved with the KEL.