PHOTONIC DEVICE

Abstract

A photonic device is configured with a photonic integrated circuit (PIC), a plurality of fiber-based gain mediums in optical communication with the PIC, and at least one optical pump outputting pump light coupled into two or more gain mediums. At least one of the fiber-based gain media and the PIC form a hybrid resonant optical cavity there between operative to lase light into the PIC. The gain media further include one or more fiber amplifiers amplifying light signals coupled into and decoupled from the PIC. The photonic device is integrated with Si photonic passive and active photonic elements, while ail fiber links between the gain media and PIC are free from these elements.

Claims

1. A photonic device comprising: a photonic integrated circuit (PIC); fiber-based gain media in optical communication with the PIC; and at least one optical pump outputting pump light coupled into and exciting the gain media.

2. The photonic device of claim 1 further comprising more than one optical pump, wherein a total number of optical pumps varies between 1 and n, wherein the n is less than a total number of the gain media

3. The photonic device of claim 1, wherein at least one of the fiber-based gain media and the PIC form a hybrid resonant optical cavity therebetween which is operative to lase light at a lasing wavelength coupled into the PIC, the resonant optical cavity being defined between a pair of reflectors.

4. The photonic device of claim 3, wherein the reflectors are integrated in the PIC, the fiber gain media forming a fiber link free from all active and passive photonic elements which are integrated in the PIC, reflectors being selected from a distributed Bragg grating, broadband coupler, directional coupler, ring mirrors, or Sagnac loop mirrors or a combination of the selected reflectors.

5. The photonic device of claim 3, wherein the resonant optical cavity is defined between: the reflectors provided in the PIC and the one fiber-based gain medium, respectively, or the reflectors written in the one fiber-based gain medium, at least one of the or both reflectors being a fiber Bragg grating.

6. The photonic device of claim 1, wherein at least one of the fiber-based gain media and the PIC form a hybrid resonant optical cavity therebetween which is operative to lase light at a lasing wavelength coupled into the PIC, the optical resonant cavity defined between the PIC and one gain medium having a ring configuration or linear configuration.

7. The photonic device of claim 6, wherein the ring-configured resonator is provided with optically interconnected within the PIC at least one or more intra-cavity filters, phase shifter, isolator optically and broadband coupler, wherein the intra-cavity filters and phase shifter provide tuning of the ring-configured resonator to a desired lasing wavelength selected from a range of wavelengths.

8. The photonic device of claim 6, wherein the ring-configured resonator is tunable, and provided with spaced apart WDM pump light input and output directional couplers, one or more ring filters, and a phase shifter, wherein one of the directional couplers, ring filters and phase shifter are integrated in the PIC and the other directional coupler is located upstream from the one gain medium.

9. The photonic device of claim 6, wherein the linearly-configured resonator is tunable and defined between two mirrors which flank one or more intra-cavity filters and a phase shifter, the filters, phase-shifter and one of the mirrors being integrated in the PIC.

10. The photonic device of claim 6, wherein the linearly-configured resonator is defined between one or more ring filters and a minor and includes an intra-cavity light splitter and phase shifter all integrated in the PIC.

11. The photonic device of claim 1, wherein the optical pump is optically coupled into the gain media outside the PIC or through the PIC.

12. The photonic device of claim 11, wherein at least one or more of the gain media and PIC form a hybrid resonant optical cavity, the gain media further including one or more fiber amplifiers which form respective fiber links free from active and passive optical elements.

13. The photonic device of claim 12, wherein the fiber amplifiers are operative amplify respective input and output signals, so that the optical device is a transceiver provided with all components of a receiver and transmitter integrated in the PIC.

14. The photonic device of claim 13, wherein the receiver is provided with the hybrid resonant cavity and the transmitter includes one or more modulators and a spatial filter, the spatial filter hemp located downstream from the output fiber amplifier in the PIC or outside thereof.

15. The photonic device of claim 1 further comprising a III-V semiconductor material gain medium in optical communication with the fiber-based gain media and bonded to or located outside the PIC.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other examples, features and functions of the inventive PIC will become more readily apparent from the specific description illustrated by the following drawings:

[0019] FIG. 1 illustrates the disclosed hybrid photonic device;

[0020] FIG. 2 is an exemplary optical schematic of the photonic device of FIG. 1;

[0021] FIG. 3 is another exemplary optical schematic of the photonic device of FIG. 1;

[0022] FIG. 4 is an optical schematic of the transceiver based on the disclosed concept;

[0023] FIGS. 5 and 6 are respective optical schematics of a transmitter based on the disclosed concept;

[0024] FIG. 7 is an optical schematic of the receiver based on the disclosed concept; and

[0025] FIGS. 8-11 are respective exemplary optical schematics of a resonant cavity utilized in the disclosed photonic device.

SPECIFIC DESCRIPTION

[0026] The following description provides an illustration and a further understanding of the inventive concept, but is not intended as a definition of the limits of the present disclosure. The following disclosure, together with the drawings, serve to explain principles and operations of the described inventive concept. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every figure.

[0027] FIG. 1 diagrammatically illustrates the inventive photonic device 10 including at least one fiber gain medium 14.sub.1. winch is the active fiber that has at least one core doped with ions of light emitters, and a PIC 12. Any of or all gain media may be configured as part of a hybrid laser 14.sub.1, as shown in FIG. 1, and/or one or more fiber amplifiers 14.sub.2. In case of the laser, a hybrid resonant cavity is formed between gain medium 14.sub.1 and PIC 12. In contrast to the prior art, the active fiber extending to PIC 12 has no photonic elements coupled thereto. In other words, the active fiber is free from photonic elements. The photonic elements may include active elements, such as polarization modules, photodiodes and optical modulators and other devices having an intended dynamic interaction between light and matter, and photonic passive elements, such as reflectors, isolators, couplers, attenuators, circulators and other known elements. Some of the passive elements can he characterized as partway between passive and active elements. All of these photonic elements are integrated in PIC 12. However, a possibility still exists to form the optical cavity in the fiber by having one or both fiber Bragg gratings (FBG) 18, 20, respectively written in the fiber. In case of one FBG, the other reflector is provided in PIC 12. If the reflector or reflectors are written in fiber, it can be advantageous to write them in a passive fiber having opposite ends thereof spliced to the output of active fiber 14; and PIC 12, respectively.

[0028] Depending on the configuration of the resonant cavity of gain medium 14.sub.1 (provided the latter is a fiber laser), all photonic passive elements including reflectors, polarization splitters, controllers and others, also maybe integrated in PIC 12. The resonant cavity of the fiber laser is defined between reflectors 18,20 which are selected from fiber Bragg gratings (FBG) and integrated in silicon ring mirrors, distributed Bragg grating, Sagnac loop mirrors, loop minors and others known in the photonic art.

[0029] In accordance with the inventive concept, photonic device 10 is configured with multiple gain media 14.sub.1, 14.sub.2 . . . and 14.sub.n with gain media 14.sub.2 . . . 14.sub.n each being configured either as a fiber laser or fiber amplifier. For example, amplifier 14.sub.2 may be an input amplifier with input fiber 14in, whereas amplifier 14n is an output amplifier with an output fiber 14out. A photonic device of the known prior art is configured with multiple fiber lasers/amplifiers energized by respective dedicated pumps in accordance with an end- or side-pumping technique. In contrast, disclosed photonic device 10 is configured with a pump 16 optically coupled to multiple gain media. Preferably, pump 16 is a single pump exciting ail three shown fiber gain media. The minimal number of pumps is application specific, but in accordance with the inventive concept, this number is always less than or equal to the number of active fibers. It may be advantageous to use a combination of fiber-based gain medium and III-V gain material 15, which is bonded to PIC 12 or located outside it, to minimize unavoidable losses in PIC 12 as signals are guided between the input and output of PIC 12.

[0030] FIG. 2 illustrates an example of photonic device 10 including a tunable fiber laser 22 with a hybrid resonant cavity, which is formed between the gain medium and PIC 12, input signal and output signal fiber amplifiers 24, 26 respectively, and pump 16. The single pump 16 is directly optically coupled to the gain media of respective laser 22 and amplifiers 24,26. After optical amplification of the output signal, a spatial filter 28 may be located downstream from output signal amplifier 26 to suppress excessive noise in the amplified output signal.

[0031] FIG. 3 illustrates a configuration similar to that of FIG. 2. However, pump 16 injects pump light into fiber laser 22 and fiber amplifiers 24,26 through PIC 12. The pump light can be coupled into the gain medium in a co-propagating direction with the signal light. Alternatively, the pump light can be coupled into a gain medium in a counter-propagating direction, as shown in FIG. 3, or both co- and counter-propagating directions. The gain media, as mentioned above, is doped with ions any of the known light emitters including rare earth elements, but for the descriptive purposes, all active fibers are shown to be doped with ions of erbium (Er).

[0032] FIG. 4 illustrates photonic device 10 which, in this example, is a transceiver used in telecommunications. The Er-doped fiber gain medium 22 and PIC 12 form a tunable Fabry-Perot resonator therebetween which is defined between at least one or more ring filter mirrors 34.sup.1, 34.sup.n and minor 36 all integrated in PIC 12. The multiple ring filter mirrors 34.sup.1, 34.sup.n are instrumental in utilizing the Vernier effect, which is a well-known technique that provides for the suppression of all lasing modes except for the desired resonant longitudinal mode. Accordingly, the hybrid resonator outputs light that can be effectively tuned by a phase shifter 40, well known to one of ordinary skill.

[0033] Characteristically, the illustrated transceiver receives an input signal carrying broadband light which is amplified by an input gain medium or fiber amplifier 24 prior to the injection thereof into PIC 12. Accordingly, illustrated photonic device 10 is configured with three gain media 22, 24 and 26, respectively all energized by single pump 16 injecting pump light into the gain media through three WDM couplers 30.

[0034] The mixing between the amplified input signal and a tapped off portion of the output lasing light in a coherent receiver 45 produces the detection of the desired information. The output light is divided in a splitter 38, which is integrated in PIC 12 downstream front partial reflectivity mirror 36, guiding the remaining portion of the lasing light toward a transmitter also integrated in PIC 12. The transmitter includes at least one modulator 42 selected from a phase or amplitude modulator. Preferably, the transmitter is configured with multiple modulators 42 receiving respective parts of the remaining portion of the output lasing light from another splitter 32. The modulated portions are collected in a combiner 34 and amplified in output signal fiber gain medium 26. The amplified modulated output light is further filtered within PIC 12 by spatial filter 28 optionally integrated in PIC 12.

[0035] FIGS. 5 and 6 illustrate a transmitter 44 configured in accordance with the inventive concept providing for multiple gain media 22,26 which receive pump light from pump 16 common to both gain mediums. The illustrated transmitter 44 can be used as a stand-alone hybrid photonic device or incorporated in the transceiver of FIG. 4.

[0036] In particular, FIG. 5 shows PIC 12 provided with the transmitter's components including the above discussed hybrid resonator between ring filter mirror 34.sup.1 . . . 34.sup.n and mirror 36, splitter 32, phase shifter 40, one or more modulators 42 and spatial filter 28 for suppressing the undesirable noise in the amplified output signal. According to the configuration of FIG. 6, the latter is not integrated in PIC 12, hut located outside PIC 12 downstream from output light fiber amplifier 26.

[0037] FIG. 7 exemplifies a receiver 46 provided with gain media 22 and 24 excited by pump light from pump 16 which is common to both gain media. The gain medium 22 and PIC 12 form a resonator in PIC 12 between ring filter mirrors 34.sup.1 . . . 34.sup.n and mirror 36. The spatial input filter 28 also integrated in PIC 12 cuts a narrow line out from broadband input light.

[0038] FIGS. 8 and 9 illustrate respective configurations of a ring resonator hybrid laser. The broadband output coupler 52 is integrated in PIC 12 and configured as a partial reflectivity mirror letting part of the light go through and another part be guided back into the cavity. It can include an adiabatic coupler and a curved coupler. One or more intra-cavity filters 48 and phase shifter 40 constitute the ring cavity and operate to tune the hybrid laser to output the desired lasing wavelength. Optionally inserted into the ring cavity is an isolator 50 controlling either a clockwise or counter-clockwise signal propagation direction in the ring cavity. Except for WDM coupler 30, all of the components mentioned above are integrated in PIC 12. The fiber of gain medium 14.sub.1 is preferably polarization-maintaining for providing the desired polarization of the light signal without a need for the polarization controller.

[0039] FIG. 9 shows a more specific implementation of the ring resonator hybrid laser shown in FIG. 8. Like in FIG. 8, here the ring resonator is defined between PIC 12 and the fiber and receives pump light from WDM broadband directional coupler 30 which is located between pump 16 and gain medium 14.sub.1. One or more ring filter mirrors 34.sub.1 . . . 34.sub.n along with phase shifter 40 provide the selection of the desired lasing wavelength, generated in response to coupling pump light at another pump wavelength into the resonant cavity through WDM 30, and all inserted the ring cavity. The output coupler 52, acting as a partial reflectivity mirror, guides the generated light at the lasing wavelength from the resonant cavity.

[0040] FIGS. 10 and 11 represent a linear architecture of the hybrid cavity. FIG. 10 illustrates the hybrid resonator defined between an FBG 56 written in the outside end of gain medium 14.sub.1 and mirror 36 which is integrated in PIC 12. The cavity tuning o the desired lasing wavelength is provided by one or more intra-cavity filters 48 and phase shifter 40. As can be seen, pump 16 and gain medium 14.sub.1 are arranged in accordance with a side pumping technique. FIG. 11 shows the hybrid resonator defined between ring filter mirrors 34.sup.1 . . . 34.sup.n and mirror 36.

[0041] Having thus described several examples, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the scope of the examples discussed herein. Accordingly, the foregoing description and drawings are by way of example only.