Integrated Optic Components Passive: Requires no input power, like directional couplers, beam splitters, isolators, filters, lenses and prisms Active: Requires input power to operate on signals, like modulators, switches, light sources and detectors Passive devices: are generally constructed by modifying the waveguide structure Integrated optics: combine many elements on a single monolithic substrate
IOC: Directional Coupler Directional coupler: formed by ion exchange, CVD, etc Operation and power ratios Ideal coupler: P 2 /P 1 =cos 2 ( L/2L c ), P 3 /P 1 =sin 2 ( L/2L c ) Coupling is a result of evanescent fields overlap L c : length for total power transfer Propagation factor matching Most common ratio is 1:1, 3dB
IOC: Active Devices Power splitters Active devices: those control light such as switching, modulation and those convert light Electro optic materilas: change their index in proportion to an applied electric field Active control requires materials that are electro optic or acousto optic
IOC: Active Components Electro optic switch Diffusing titanium into lithium niobate (strong electro optic effect) Operation Acousto optic materials rely on the interaction between acoustic waves, excited piezo electrically at WG surface and light beam
IOC: Active Components Modulator Mach-Zehnder interferometer Operation Devices operating at GHz range and requires 10 V is available Transfer characteristic of a switch is: P o /P in =0.5(1+cos V/V ) V :voltage produces 180 o phase shift Nonlinear operation is not desired
IOC: Active Components It operates around linear portions by replacing V by V- V /2 P o /P in =0.5(1+sin V/V ) Advantages of external modulators and switches: Higher frequency Does not vary source wavelength and linewidth
Optoelectronic Integrated Circuits OIC: combining optical and electronic functions on same substrate GaAs substrate GaAs Photoconductive detector GaAs MESFET AlGaAs Laser diode
AWG
Planar FBG
Spectrum