Abstract:
A display includes a display modulation layer (116), a backlight unit (118) configured to generate light for illumination of the display modulation layer (116), and a filter film (120) disposed between the backlight unit (118) and the display modulation layer (116). The filter film (120) includes a plurality of Bragg grating sets. Each Bragg grating set is configured to reflect the light (138, 140) in a wavelength-selective and angular-selective manner rearward toward the backlight unit (118).
Abstract:
An optical modulator includes a dielectric waveguide (210) for receiving an optical beam (225) and coupling energy of the optical beam into the waveguide. At least one Stark material is provided in the waveguide. A bias circuit generates a bias signal to produce an electrical field across the Stark material to shift at least one of the Stark absorption frequencies towards the frequency of the optical beam. A circuit for producing a time varying electric field across the Stark material modulates the optical beam. The electric fields are produced between electrodes (215) provided on the outside of the waveguide. At least a portion of the bias field can be generated by an alternating bias signal, such as a square wave. A method of modulating optical signals includes the steps of providing a dielectric waveguide for receiving an optical beam and coupling energy of the optical beam into the waveguide, the waveguide having at least one Stark material disposed therein, and varying an electric field imposed across the Stark material.
Abstract:
An optical modulator 1 has an optical input signal waveguide 2, first and second interferometric waveguide arms 6, 8, a modulated output signal waveguide 12, a splitter 4 for dividing the input optical signal between the first and second arms 6, 8, and a combiner 10 for re-combining the signals transmitted along each of the first and second arms 6, 8 into the output signal waveguide 12. The modulator 1 further has first and second electrodes 14, 16 each of a segmented structure having a plurality of elements 18, 20 each extending from a respective one of the first and second electrodes 14, 16. The elements 18, 20 of each of the first and second electrodes 14, 16 each have a first part 30, 32 positioned such as to have an electro optic effect on a signal transmitted through the corresponding one of the first and second arms 6, 8 and at least a proportion of the elements 18, 20 of the first electrode 14 each have a second part 34 positioned such as to have limited or no electro optic effect on a signal transmitted through the first arm 6.
Abstract:
A semiconductor-based optical modulator is presented that includes a separate phase control section to adjust the amount of chirp present in the modulated output signal. At least one section is added to the modulator configuration and driven to create a pure "phase" signal that will is added to the output signal and modify the e if term inherent in the modulation function. The phase modulation control section may be located within the modulator itself (with one segment on each arm, driven by the same input signal), or may be disposed "outside" of the modulator on either the input waveguiding section or the output waveguiding section. The phase control section may be formed to comprise multiple segments (of different lengths), with the overall phase added to the propagating signal controlled by selecting the different segments to be energized to impart a phase delay to a signal propagating through the energized section(s).
Abstract:
The device is based on a cross-correlator which measures the signal between a pair of oppositely chirped laser pulses. Two laser pulses, one with a positive chirp and one with a negative chirp, are mixed on a beamsplitter. The two resulting beams pass through a reference or a sample arm and are subsequently mixed on a non-lmear crystal. The signal from the interferometer is the sum frequency generation produced in that crystal. The reference arm contains a moveable delay which is used to change the relative timing of the two beams in the interferometer. The sum frequency generation in the narrow band of frequencies is the signal from the device and is measured as a function of the delay. Alternatively, a pure dispersive phase shift could be used in place of the two laser pulses.
Abstract:
The invention relates to an electroabsorption modulator (EAM) (300), comprising a first EAM section (302) optically coupled to a second EAM section (304), a transition wavelength in the electroabsorption (EA) spectrum of the first EAM section (302), at which absorption changes substantially, being different to a transition wavelength in the EA spectrum of the second EAM section (304). The EAM (300) compensates for chirp (which is caused by intrinsic absorption effects) by driving the two sections with a signal (312) generated from a common modulating signal (314). The driving signal (312) at the first EAM section (302) being preferably in anti-phase with the driving signal (312) at the second EAM section (304).
Abstract:
An electrically tunable optical modulator includes a substrate having an electrooptical effect, an optical waveguide having first, second, and third cascading portions in the substrate, and transmitting an optical field, a first coplanar waveguide electrode having a first part over the first cascading portion and second and third parts extending beyond the first cascading portion, a second coplanar waveguide electrode having a fourth part over the second cascading portion and fifth and sixth parts extending beyond the second cascading portion, a third coplanar waveguide electrode having a seventh part over the third cascading portion and eighth and ninth parts extending beyond the third cascading portion, a fourth coplanar waveguide electrode formed to have a first distance from the first coplanar waveguide electrode, a fifth coplanar waveguide electrode formed between the first and second coplanar waveguide electrodes to have second and third distances, respectively, a sixth coplanar waveguide electrode formed between the second and third coplanar waveguide electrodes to have fourth and fifth distances, respectively, a seventh coplanar waveguide electrode formed to have a sixth distance from the third coplanar waveguide electrode, and a voltage source supplying voltages to the first, second, and third coplanar waveguide electrodes, wherein the fourth to seventh coplanar waveguide electrodes are grounded and the first to sixth distances are substantially the same, so that electrooptic overlap integrals of each cascading portion of the optical waveguide are the same.
Abstract:
An integrated optical modulator of the Mach-Zehnder type has a waveguide which, for part of its length, is divided into two waveguide sections (11, 12) arranged logically in parallel. Incoming light is divided to pass along the two sections (11, 12) and is then recombined before leaving the modulator. Each waveguide section has a pair of electrodes (13, 14) and (14, 15) associated therewith to generate an electric field through which the respective waveguide section passes, though there may be a single electrode (14) between the two waveguide sections (11, 12) to serve as one electrode of each pair, with the other electrode of each pair commoned. The physical arrangement of one waveguide section (11) and its associated electrodes (13, 14) is different from that of the other waveguide section (12) and its associated electrodes (14, 15), such that the electric fields to which light propagated along the two waveguide sections (11, 12) are respectively subjected are different when a single driving voltage is applied to the electrodes (13, 14, 15) associated with the waveguide sections. In an alternative arrangement there is provided an amplitude modulator (30) followed by a phase modulator (31).