A grating coupler having first and second ends for coupling a light beam to a waveguide of a chip includes a substrate configured to receive the light beam from the first end and transmit the light beam through the second end, the substrate having a first refractive index n1, a grating structure having curved grating lines arranged on the substrate, the grating structure having a second refractive index n1, wherein the curved grating lines have line width w and height d and are arranged by a pitch , wherein the second refractive index n2 is less than first refractive index n1, and a cladding layer configured to cover the grating structure, wherein the cladding layer has a third refractive index n3.

A system includes a surface coupled edge emitting laser that includes a core waveguide, a fan out region optically coupled to the core waveguide in a same layer of the surface coupled edge emitting laser as the core waveguide; and a first surface grating formed in the fan out region; and a photonic integrated circuit (PIC) that includes an optical waveguide and a second surface grating formed in an upper layer of the PIC, wherein the second surface grating is in optical alignment with the first surface grating.

An in-plane-emitting semiconductor diode laser employs a surface-trapped optical mode existing at a boundary between a distributed Bragg reflector and a homogeneous medium, dielectric or air. The device can operate in both TM-polarized and TE-polarized modes. The mode exhibits an oscillatory decay in the DBR away from the surface and an evanescent decay in the dielectric or in the air. The active region is preferably placed in the top part of the DBR close to the surface. The mode behavior strongly depends on the wavelength of light, upon increase of the wavelength the mode becomes more and more extended into the homogeneous medium, the optical confinement factor of the mode in the active region drops until the surface-trapped mode vanishes. Upon a decrease of the wavelength, the leakage loss of the mode into the substrate increases. Thus, there is an optimum wavelength, at which the laser threshold current density is minimum, and at which the lasing starts. This optimum wavelength is temperature-stabilized, and shifts upon temperature increase at a low rate less than 0.1 nm/K, indicating wavelength-stabilized operation of the device. The approach applies also to semiconductor optical amplifiers or semiconductor gain chips which are also wavelength-stabilized. Reflectivity of the surface-trapped mode from an uncoated facet of the device can be extremely low, also <1E-4 or even <1E-5 which is particularly advantageous for amplifiers or gain chips. For diode lasers, a specific intermediate reflective coating can be deposited on the facet to put its reflectivity into a range from 0.5% to 3%, which lies within targeted values for lasers. An optical integrated circuit can employ wavelength-stabilized amplifiers operating in a surface-trapped mode, wherein such devices amplify light propagating along a dielectric waveguide.

An in-plane-emitting semiconductor diode laser employs a surface-trapped optical mode existing at a boundary between a distributed Bragg reflector and a homogeneous medium, dielectric or air. The device can operate in both TM-polarized and TE-polarized modes. The mode exhibits an oscillatory decay in the DBR away from the surface and an evanescent decay in the dielectric or in the air. The active region is preferably placed in the top part of the DBR close to the surface. The mode behavior strongly depends on the wavelength of light, upon increase of the wavelength the mode becomes more and more extended into the homogeneous medium, the optical confinement factor of the mode in the active region drops until the surface-trapped mode vanishes. Upon a decrease of the wavelength, the leakage loss of the mode into the substrate increases. Thus, there is an optimum wavelength, at which the laser threshold current density is minimum, and at which the lasing starts. This optimum wavelength is temperature-stabilized, and shifts upon temperature increase at a low rate less than 0.1 nm/K, indicating wavelength-stabilized operation of the device. The approach applies also to semiconductor optical amplifiers or semiconductor gain chips which are also wavelength-stabilized. Reflectivity of the surface-trapped mode from an uncoated facet of the device can be extremely low, also <1E4 or even <1E5 which is particularly advantageous for amplifiers or gain chips. For diode lasers, a specific intermediate reflective coating can be deposited on the facet to put its reflectivity into a range from 0.5% to 3%, which lies within targeted values for lasers. An optical integrated circuit can employ wavelength-stabilized amplifiers operating in a surface-trapped mode, wherein such devices amplify light propagating along a dielectric waveguide.

A tunable laser includes a reflective semiconductor optical amplifier (SOA), a grating codirectional coupler, and a reflective microring resonator. The grating codirectional coupler and the reflective microring resonator are both formed on a silicon base. An anti-reflection film is disposed on a first end surface of the reflective SOA, and the first end surface is an end surface, coupled to a first waveguide of the grating codirectional coupler, of the reflective SOA. A second waveguide of the grating codirectional coupler is coupled to the first waveguide, a first grating is disposed on the first waveguide, a second grating disposed opposite to the first grating is disposed on the second waveguide, and the first grating and the second grating constitute a narrow-band pass filter. The second waveguide is connected to the reflective microring resonator.

A grating coupler having first and second ends for coupling a light beam to a waveguide of a chip includes a substrate configured to receive the light beam from the first end and transmit the light beam through the second end, the substrate having a first refractive index n1, a grating structure having curved grating lines arranged on the substrate, the grating structure having a second refractive index n1, wherein the curved grating lines have line width w and height d and are arranged by a pitch , wherein the second refractive index n2 is less than first refractive index n1, and a cladding layer configured to cover the grating structure, wherein the cladding layer has a third refractive index n3.

A grating coupler having first and second ends for coupling a light beam to a waveguide of a chip includes a substrate configured to receive the light beam from the first end and transmit the light beam through the second end, the substrate having a first refractive index n1, a grating structure having curved grating lines arranged on the substrate, the grating structure having a second refractive index n1, wherein the curved grating lines have line width w and height d and are arranged by a pitch , wherein the second refractive index n2 is less than first refractive index n1, and a cladding layer configured to cover the grating structure, wherein the cladding layer has a third refractive index n3.

A grating coupler having first and second ends for coupling a light beam to a waveguide of a chip includes a substrate configured to receive the light beam from the first end and transmit the light beam through the second end, the substrate having a first refractive index n1, a grating structure having curved grating lines arranged on the substrate, the grating structure having a second refractive index n1, wherein the curved grating lines have line width w and height d and are arranged by a pitch , wherein the second refractive index n2 is less than first refractive index n1, and a cladding layer configured to cover the grating structure, wherein the cladding layer has a third refractive index n3.

A system includes a surface coupled edge emitting laser that includes a core waveguide, a fan out region optically coupled to the core waveguide in a same layer of the surface coupled edge emitting laser as the core waveguide; and a first surface grating formed in the fan out region; and a photonic integrated circuit (PIC) that includes an optical waveguide and a second surface grating formed in an upper layer of the PIC, wherein the second surface grating is in optical alignment with the first surface grating.

An optoelectronic device employs a surface-trapped TM-polarized optical mode existing at a boundary between a distributed Bragg reflector (DBR) and a homogeneous medium, dielectric or air. The device contains a resonant optical cavity surrounded by two DBRs, and an additional DBR section on top supporting the surface-trapped mode. Selective chemical transformation, like selective oxidation, etching or alloy composition intermixing form a central core and a periphery having different vertical profiles of the refractive index. Therefore, the longitudinal VCSEL mode in the core is non-orthogonal to the surface-trapped mode in the periphery, and the two modes can be transformed into each other. Such transformation allows fabrication of a number of optoelectronic devices and systems like a single transverse mode VCSEL, an integrated optical circuit operating as an optical amplifier, an integrated optical circuit combining a VCSEL and a resonant cavity photodetector, etc.