WAVEGUIDE TYPE OPTICAL MODULATOR

• Main Authors: ICHIKAWA TOMONORI, YASUMA YASUHIRO
• Format: Patent
• Language: English
• Published: 20.06.1997
• Edition: 6
• Subjects: DEVICES OR ARRANGEMENTS, THE OPTICAL OPERATION OF WHICH ISMODIFIED BY CHANGING THE OPTICAL PROPERTIES OF THE MEDIUM OF THEDEVICES OR ARRANGEMENTS FOR THE CONTROL OF THE INTENSITY,COLOUR, PHASE, POLARISATION OR DIRECTION OF LIGHT, e.g.SWITCHING, GATING, MODULATING OR DEMODULATING; FREQUENCY-CHANGING; NON-LINEAR OPTICS; OPTICAL ANALOGUE/DIGITAL CONVERTERS; OPTICAL LOGIC ELEMENTS; OPTICS; PHYSICS; TECHNIQUES OR PROCEDURES FOR THE OPERATION THEREOF

PROBLEM TO BE SOLVED: To substantially prevent a DC(direct current) drift from being generated by making it possible to freely set an operation point at an arbitrary position without applying any DC bias voltage. SOLUTION: This modulator is equipped with a waveguide type optical device 38 which has a waveguide 34 with a branch part 32 in a closed loop shape formed on a waveguide substrate 30 having electrooptic effect and also has electrodes 36a and 36b formed on both branch waveguides 34a and 34b at a branch part 32 and a driving circuit 40 which applies an alternating driving voltage between both the electrodes 36a and 36b, and controls the intensity of projection light by the driving circuit 40 according to the difference between the potentials applied to the electrodes 36a and 36b. At a portion of one branch waveguide 34b of the waveguide type optical device 38, a phase shift part 37 which makes use of photorefractive effect is provided and the phase of waveguide light is shifted by adjusting the intensity of the incident light to impose light intensity modulation only by applying the alternating driving voltage by the single driving circuit without requiring any DC bias voltage.