KR102396079B1 - distributed feedback(DFB) laser diode - Google Patents

Abstract

The present invention discloses a distributed feedback laser diode. A laser diode thereof comprises a substrate having distribution regions, a lower clad layer on the substrate, Bragg diffraction gratings disposed in the lower clad layer over the distribution regions, a waveguide disposed on the lower clad layer, and a waveguide disposed on the waveguide. and an upper clad layer formed on the upper clad layer, and electrodes on the upper clad layer.

Description

Distributed feedback (DFB) laser diode

The present invention relates to a laser diode, and more particularly to a distributed feedback laser diode capable of generating mode-locked laser light.

Among semiconductor-based optical devices, functional laser devices that select a specific wavelength, such as a distributed feedback laser diode and/or a distributed Bragg reflector laser diode, are being developed. These functional laser devices may perform wavelength filtering using a diffraction grating. For example, only the light wave having a specific wavelength corresponding to the Bragg wavelength due to the periodic refractive index change of the light wave may be reflected. Thereby, wavelength filtering can be achieved. The reflected light wave of a specific wavelength may be oscillated by being fed back to the gain region.

An object of the present invention is to provide a distributed feedback laser diode capable of generating a mode-locked laser light having a wide bandwidth of 5 nm or more.

The present invention discloses a distributed feedback laser diode. The laser diode thereof comprises: a substrate having a first distribution region, a first gain region, a phase region, a second gain region and a second distribution region; a lower clad layer disposed on the substrate; first and second Bragg diffraction gratings disposed in the lower clad layer on the first distribution region and the second distribution region; a waveguide disposed on the lower clad layer and extending from the first distribution area to the second distribution area; an upper clad layer disposed on the waveguide; and first to fifth electrodes respectively disposed on the upper clad layer of the first distribution region, the first gain region, the phase region, the second gain region, and the second distribution region. Each of the first and second Bragg diffraction gratings may have a length of 0.1 μm to 50 μm in a direction parallel to the substrate and the waveguide.

As described above, the distributed feedback laser diode according to the concept of the present invention can generate mode-locked laser light with a wide bandwidth of 5 nm or more using the first and second Bragg diffraction gratings with a length of about 0.1 μm to 50 μm. there is.

1 is a cross-sectional view showing a distributed feedback laser diode according to the concept of the present invention.
2 is a graph showing a change in the bandwidth of laser light according to the length of first and second Bragg diffraction gratings.
3 is a graph showing the bandwidth of laser light formed by first and second Bragg diffraction gratings of 50 μm long.
4 is a graph showing the bandwidth of laser light formed in the first and second Bragg diffraction gratings 32 and 34 having a length of 200 μm.
5 is a graph showing the bandwidth of laser light formed in the first and second Bragg diffraction gratings 32 and 34 having a length of 300 μm.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Advantages and features of the present invention, and a method for achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments described herein, and may be embodied in different forms. Rather, the embodiments introduced herein are provided so that the disclosed content may be thorough and complete and the spirit of the present invention may be sufficiently conveyed to those skilled in the art, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

The terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, a referenced component, step, operation and/or apparatus includes and/or includes excludes the presence or addition of one or more other components, steps, operations and/or elements. I never do that. Also, in the specification, mode locking may be understood as a meaning mainly used in the laser field. Since it is according to a preferred embodiment, reference signs provided in the order of description are not necessarily limited to the order.

1 shows a distributed feedback (DFB) laser diode 100 according to the concept of the present invention.

Referring to FIG. 1 , the DFB laser diode 100 of the present invention includes a substrate 10 , a lower clad layer 20 , first and second Bragg diffraction gratings 32 and 34 , a waveguide 40 , and an upper clad layer. layer 50 , first to fifth electrodes 61 - 65 , and first and second anti-reflective coating layers 72 , 74 .

The substrate 10 may include InP. According to an example, the substrate 10 may have a first distribution region D1, a first gain region G1, a phase region P, a second gain region G2, and a second distribution region D2. can The substrate 10 may be grounded.

The lower clad layer 20 may be disposed on the substrate 10 . The lower clad layer 20 may have a refractive index higher than that of the substrate 10 and lower than a refractive index of the waveguide 40 . For example, the lower clad layer 20 may include n-type InP.

The first and second Bragg diffraction gratings 32 and 34 may be respectively disposed in the lower clad layer 20 of the first and second distribution regions D1 and D2. Each of the first and second Bragg diffraction gratings 32 and 34 may include p-type InP, InGaAs, or a cavity. For example, each of the patterns 36 of the first and second Bragg diffraction gratings 32 and 34 may have a width or length of about 0.1 μm.

The waveguide 40 may be disposed on the lower clad layer 20 . The waveguide 40 may be spaced apart from the first and second Bragg diffraction gratings 32 and 34 in a direction perpendicular to the substrate 10 . The waveguide 40 may extend in a direction parallel to the substrate 10 . The waveguide 40 may include intrinsic InP. For example, the waveguide 40 may include active waveguides 42 and passive waveguides 44 . The active waveguides 42 may be disposed on the first distribution area D1 , the first gain area G1 , the second gain area G2 , and the second distribution area D2 . Although not shown, the active waveguides 42 may include impurities for obtaining a gain of the laser light 80 . The passive waveguide 44 may be connected between the active waveguides 42 . The passive waveguide 44 may be disposed on the lower clad layer 20 in the phase region P.

The upper clad layer 50 may be disposed on the waveguide 40 . The upper clad layer 50 may include n-type InP. The upper clad layer 50 may have a lower refractive index than that of the waveguide 40 .

The first to fifth electrodes 61 - 65 include a first distribution region D1 , a first gain region G1 , a phase region P, a second gain region G2 , and a second distribution region D2 . ) may be respectively disposed on the upper clad layer 50 . The first to fifth electrodes 61 - 65 may provide current to the substrate 10 . The current may electrically change refractive indices of the lower clad layer 20 , the waveguide 40 , and the upper clad layer 50 .

The first and second anti-reflection coating layers 72 and 74 may be disposed on both sidewalls of edges of the lower clad layer 20 , the waveguide 40 , and the upper clad layer 50 . When a current is applied to at least one of the first to fifth electrodes 61 to 65 , the laser light 80 may be generated along the waveguide 40 . The first and second anti-reflective coating layers 72 and 74 may resonate the laser light 80 . The laser light 80 may pass through any one of the first and second anti-reflection coating layers 72 and 74 to be output to the outside.

When a first current is applied to the second electrode 62 and the fourth electrode 64 , the active waveguides 42 may obtain a gain of the laser light 80 . The intensity of the laser light 80 may be proportional to the first current.

When a second current is applied to the third electrode 63 , the phase of the laser light 80 may be modulated. The second current may electrically change the refractive index of the passive waveguide 44 in the phase region P to tune the wavelength of the laser light 102 .

When a third current is applied to the first electrode 61 and the fifth electrode 65 , mode locking of the laser light 80 may be generated. The mode locking is an optical technique capable of generating pulses of laser light 80 of very short duration, on the order of picoseconds (10 ^-12 s) or femtoseconds ((10 ^-15 s). The mode-locked laser As the bandwidth of the light 80 increases, the communication channel and/or transmission capacity may increase.

Meanwhile, the bandwidth of the laser light 80 may be changed according to the length ℓ of the first and second Bragg diffraction gratings 32 and 34 .

2 shows the change in the bandwidth of the laser light 80 with the length l of the first and second Bragg diffraction gratings 32 and 34 .

Referring to FIG. 2 , the bandwidth of the laser light 80 may be inversely proportional to the length ℓ of each of the first and second Bragg diffraction gratings 32 and 34 . If the length l of the first and second Bragg diffraction gratings 32 and 34 is decreased, the bandwidth of the laser light 80 may increase. The length l of the first and second Bragg diffraction gratings 32 and 34 may be greater than the width and/or length of the pattern 36 .

3 shows the bandwidth of the laser light 80 formed by the first and second Bragg diffraction gratings 32 , 34 of 50 μm length l.

2 and 3 , when the length ℓ of the first and second Bragg diffraction gratings 32 and 34 is about 50 μm, the laser light 80 may have a bandwidth of about 5 nm. . Bandwidth may be defined as the width and/or distance of peaks of laser light 80 having an intensity of 30 dB or greater. When the length ℓ of the first and second Bragg diffraction gratings 32 and 34 is reduced to about 50 μm or less, the bandwidth of the laser light 80 may increase to 5 nm or more.

Referring back to FIG. 2 , when the length ℓ of the first and second Bragg diffraction gratings 32 and 34 is increased to about 100 μm or more, the bandwidth of the laser light 80 is increased by the distributed Bragg reflection (DBR). : It can be reduced to about 2nm or less by dispersion of Distributed Bragg Reflection.

4 shows the bandwidth of the laser light 80 formed in the first and second Bragg diffraction gratings 32 and 34 of 200 μm length (l).

2 and 4 , when the length ℓ of the first and second Bragg diffraction gratings 32 and 34 is about 200 μm, the laser light 80 has a bandwidth of about 1.5 nm. can

Fig. 5 shows the bandwidth of the laser light 80 formed in the first and second Bragg diffraction gratings 32, 34 of 300 μm long (l).

2 and 5 , when the length ℓ of the first and second Bragg diffraction gratings 32 and 34 is about 300 μm, the laser light 80 may have a bandwidth of about 1 nm. there is.

The contents described above are specific examples for carrying out the present invention. The present invention will include not only the above-described embodiments, but also simple design changes or easily changeable embodiments. In addition, the present invention will also include techniques that can be easily modified and implemented in the future using the above-described embodiments.

Claims (10)

a substrate having a first distribution region, a first gain region, a phase region, a second gain region, and a second distribution region;
a lower clad layer disposed on the substrate;
first and second Bragg diffraction gratings disposed in the lower clad layer on the first distribution region and the second distribution region;
a waveguide disposed on the lower clad layer and extending from the first distribution area to the second distribution area;
an upper clad layer disposed on the waveguide; and
first to fifth electrodes respectively disposed on the upper clad layer of the first distribution region, the first gain region, the phase region, the second gain region, and the second distribution region;
Each of the first and second Bragg diffraction gratings has a length of 0.1 μm to 50 μm in a direction parallel to the substrate and the waveguide.
The method of claim 1,
each of the first and second Bragg diffraction gratings includes grating patterns.
delete The method of claim 1,
The waveguide includes:
passive waveguide; and
A distributed feedback laser diode comprising active waveguides disposed on both sides of the passive waveguide.
5. The method of claim 4,
The passive waveguide is a distributed feedback laser diode disposed in the phase region.
5. The method of claim 4,
wherein the active waveguides are disposed in the first and second distribution regions and the first and second gain regions.
The method of claim 1,
The waveguide includes a distributed feedback laser diode including intrinsic indium phosphorus (InP).
The method of claim 1,
The lower cladding layer is a distributed feedback laser diode including n-type indium phosphorus (n-InP).
The method of claim 1,
The first and second Bragg diffraction gratings include a p-type indium phosphorus (p-InP) distributed feedback laser diode.
The method of claim 1,
and first and second anti-reflection coating layers respectively disposed on both sidewalls of the substrate, the lower clad layer, the waveguide, and the upper clad layer.

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