Planar optical device

Claim 1

An optical device, comprising: a) an elongate, active glass core which extends along a longitudinal axis and comprises silicon, oxygen, and erbium, the erbium being at least partially in the form of Er³⁺ ions, the active core having a refractive index; b) a glass cladding comprising at least one layer which at least partially surrounds the active core and has a refractive index which is smaller than the core refractive index; c) means for coupling signal radiation, having a signal wavelength, into the active core and means for coupling the signal radiation out of the active core; and d) means for coupling pump radiation into the active core such that pump radiation of an appropriate wavelength will excite at least some of the Er³⁺ ions to a lasing level, leading to amplification of the signal radiation by stimulated emission, CHARACTERIZED IN THAT e) the device further comprises a substrate having a substantially planar principal surface; f) the active core is a body that overlies a portion of the principal surface; g) the cladding comprises a lower cladding layer disposed between the active core and the principal surface, and an upper cladding layer which overlies and partially surrounds the active core; h) the active core further comprises an alkali metal or alkaline earth metal in an effective quantity to prevent clustering of erbium atoms; i) the active core has an erbium-to-silicon atomic ratio of at least about 0.01 and an absolute erbium concentration of at least about 1.4 x 10²⁰ atoms per cubic centimeter, and j) the lasing level has a radiative lifetime of at least about 7 ms.

Claim 14

A method for forming an optical device on a substrate having a substantially planar principal surface, comprising: a) forming a first layer of vitreous silicon dioxide on the principal surface; b) depositing a second layer of silica-based glass over the first layer by sputtering a target of silica-based glass such that the second layer has a higher refractive index than the first layer, c) annealing the second layer such that it is stabilized; d) removing a portion of the second layer by etching, such that an elongate core, extending along the longitudinal axis, is formed, the core being adapted, after completion of the device, to guide electromagnetic radiation of at least a signal wavelength and a pump wavelength; and e) depositing a third layer of phosphosilicate glass over the core such that the third layer has a smaller refractive index than the core; CHARACTERIZED IN THAT f) the target further comprises sodium and erbium; and g) the target composition is selected such that the core has an erbium-to-silicon atomic ratio of at least about 0.01, a sodium-to-silicon atomic ratio in the approximate range 0.2 - 0.6, and an absolute erbium concentration of at least about 1.4 x 10²⁰ atoms per cubic centimeter, and the target composition is further selected such that a lasing level is associated with the erbium in the core, the lasing level having a radiative lifetime of at least about 7 ms.

Claim 18

A method for forming an optical device on a substrate having a substantially planar principal surface, comprising: a) forming a first layer of silicon dioxide on the principal surface; b) depositing a second layer of phosphosilicate glass over the first layer such that the second layer has a higher refractive index than the first layer; c) annealing the second layer such that it is at least partially densified; d) removing a portion of the second layer by etching, such that an elongate lower core having a longitudinal axis is formed, the lower core being adapted, after completion of the device, to guide electromagnetic radiation of at least a signal wavelength and a pump wavelength; e) annealing the lower core such that roughness due to etching of the second layer is substantially removed; f) depositing a third layer of silica-based glass over the lower core by sputtering a target of silica-based glass such that the third layer has a higher refractive index than the lower core; g) annealing the third layer such that it is stabilized; h) removing a portion of the third layer by etching, such that an elongate upper core, extending along the longitudinal axis, is formed, the upper core being adapted, after completion of the device, to guide electromagnetic radiation of the signal and pump wavelengths; i) annealing the upper core at a temperature of at least about 700°C for a duration of at least about 1 hour in a reactive atmosphere; and j) depositing a fourth layer of phosphosilicate glass over the upper and lower cores such that the fourth layer has a smaller refractive index than the upper and lower cores; CHARACTERIZED IN THAT k) the target further comprises sodium and erbium; and l) the target composition is selected such that the third layer has an erbium-to-silicon atomic ratio of at least about 0.01, a sodium-to-silicon atomic ratio in the approximate range 0.2 - 0.6, and an absolute erbium concentration of at least about 1.4 x 10²⁰ atoms per cubic centimeter, and the target composition is further selected such that a lasing level is associated with the erbium in the third layer, the lasing level having a radiative lifetime of at least about 7 ms.