Magnetic field generator for optical devices utilizing magneto-optical effect, and method of fabricating base substrate thereof

A method of fabricating a base substrate for a magnetic field generator, including coils formed on a silicon substrate and a structure to hold magnetic objects, the method comprising the steps of:

• (a) forming an insulation film on top and bottom sides of the silicon substrate, and partly removing the bottom-side insulation film to create an opening at a place where a hollow will be made;
• (b) etching the silicon substrate using the bottom-side insulation film as an etching mask to produce a hollow as deep as the thickness of the silicon substrate, whereby the top-side insulation film remains unetched at the bottom of the produced hollow;
• (c) forming a conductive thin film in a spiral pattern on the top side of the insulated silicon substrate, stacking an insulating thin film thereon, and partly removing the insulating thin film to create openings for coil terminals, electric contacts, and upper hollows;
• (d) forming another layer of the conductive thin film in a spiral pattern, stacking another layer of the insulating thin film thereon, and partly removing the insulating thin film to create openings for the coil terminals and upper hollows;
• and
• (e) removing the top-side insulation layer remaining in the hollows.

A variable optical attenuator which receives a multiplexed optical signal and outputs the same after attenuating each optical component contained therein, comprising:

• a lens which turns a given optical signal into a collimated beam;
• a first dispersion device which causes spectral dispersion of the collimated beam to obtain individual wavelength components thereof;
• a second dispersion device which renders the individual wavelength components parallel, thereby producing a parallel light beam;
• a birefringent crystal which causes polarization splitting of the parallel light beam;
• and
• a magnetic field generator which applies a magnetic field to the parallel light beam has passed through said birefringent crystal, comprising:
• an insulating substrate made of non-magnetic material, having a plurality of hollows,
• a plurality of coils formed on said insulating substrate in alignment with the hollows, each having at least one layer of conductive film shaped in a spiral pattern,
• a plurality of main magnetic cores made of magnetic material, each of which is mounted on said insulating substrate, partly fitting into the hollows,
• a target device held on said insulating substrate, which is exposed in a combined magnetic field produced by said plurality of main magnetic cores, and
• a permanent magnet held on said insulating substrate, which applies a magnetic field to said target device so as to bring about magnetic saturation thereof.

An optical device which equalizes the intensity of different wavelength components contained in a multiplexed optical signal, comprising:

• (a) an optical fiber cable carrying the multiplexed optical signal;
• (b) an optical amplifier which amplifies the multiplexed optical signal;
• (c) an optical coupler which splits a fraction of the multiplexed optical signal that is amplified by said optical amplifier;
• (d) a multi-channel optical monitor, coupled to said optical coupler, which measures the intensity of each spectral component contained in the fraction of the multiplexed optical signal;
• (e) a controller, coupled to said multi-channel optical monitor, which produces electrical signals according to the measured intensity of each spectral component;
• (f) an optical circulator having a first to third ports to route one optical signal from the first port to the second port and another optical signal from the second port to the third port, the first port being coupled to said optical coupler;
• (g) a variable optical attenuator which gives an attenuation to each spectral component of the multiplexed optical signal received from the second port of said optical circulator, as specified by the electrical signals supplied from said controller, and sends the resulting equalized optical signal back to the second port of said optical circulator, and which comprises:
• (g1) a lens which turns a given optical signal into a collimated beam,
• (g2) a first dispersion device which causes spectral dispersion of the collimated beam to obtain individual wavelength components thereof,
• (g3) a second dispersion device which renders the individual wavelength components parallel, thereby producing a parallel light beam,
• (g4) a birefringent crystal which causes polarization splitting of the parallel light beam, and
• (g5) a magnetic field generator which applies a magnetic field to the parallel light beam that has passed through said birefringent crystal, comprising:
• (g5a) an insulating substrate made of nonmagnetic material, having a plurality of hollows,
• (g5b) a plurality of coils formed on said insulating substrate in alignment with the hollows, each having at least one layer of conductive film shaped in a spiral pattern,
• (g5c) a plurality of main magnetic cores made of magnetic material, each of which is mounted on said insulating substrate, partly fitting into the hollows,
• (g5d) a target device held on said insulating substrate, which is exposed in a combined magnetic field produced by said plurality of main magnetic cores, and
• (g5e) a permanent magnet held on said insulating substrate, which applies a magnetic field to said target device so as to bring about magnetic saturation thereof.