Micro-fabrication of advanced photonic devices by means of direct point-by-point femtosecond inscription in silica

Abstract

We present recent results on experimental micro-fabrication and numerical modeling of advanced photonic devices by means of direct writing by femtosecond laser. Transverse inscription geometry was routinely used to inscribe and modify photonic devices based on waveguiding structures. Typically, standard commercially available fibers were used as a template with a pre-fabricated waveguide. Using a direct, point-by-point inscription by infrared femtosecond laser, a range of fiber-based photonic devices was fabricated including Fiber Bragg Gratings (FBG) and Long Period Gratings (LPG). Waveguides with a core of a couple of microns, periodic structures, and couplers have been also fabricated in planar geometry using the same method.

Femtosecond laser microfabrication of subwavelength structures in photonics

“…Nonlinear propagation of the femtosecond laser pulses in gaseous and solid transparent dielectric media is a fundamental physical phenomenon in a wide range of important applications such as laser lidars, laser micromachining (ablation) and microfabrication etc. These applications require very high intensity of the laser field, typically 10 12 -10 15 TW/cm 2 . Such high intensity leads to significant ionization and creation of electron-hole plasma.…”

Model of the femtosecond laser inscription by a single pulse

“…However, due to the fast free electron generation via MPA, plasma defocusing and absorption may arrest the collapse. Interplay of these effects has been suggested as useful for 'one-step' fabrication of subwavelength or geometrically complex refractive index changes (Mezentsev et al 2006a). Here, both the subcritical, P < P cr , and critical regimes, P > P cr , of self-focusing defined by P cr = λ 2 0 /(2πnn 2 ), where λ is the laser wavelength, n is the linear and n 2 the nonlinear refractive index of silica, are studied.…”

Fabrication of high quality optical coherence tomography (OCT) calibration artefacts using femtosecond inscription

“…*leegcb@aston.ac.uk; phone +44 121 204 3498; fax +44 1212043682; www.aston.ac.uk With the advent of the femtosecond laser (fs) it is now possible to directly perform high-resolution micromachining and inscription in a wide range of planar and fibre devices [10]. Fs laser inscription has been applied to some tough materials such as diamond [11], ceramic [12] and silica [13]. The interaction between the ultrashort laser pulse and a material is largely due to a nonlinear process whereby multi-photon absorption is dominant [10].With a suitable numerical aperture machining lens, machining translation speed and energy per pulse it is possible to create extremely localised changes around the laser focal spot within a material [14].…”