KR20080096634A - Method for generation of terahertz waves using distributed feedback laser device - Google Patents

Abstract

A method for generating terahertz waves using a DFB(Distributed feedback) laser device is provided to change difference between two mode frequencies emitted from a multiregional DFB laser device from a low frequency to a THz region by changing period difference of a diffraction grating. A first diffraction grating is formed in a first DFB region including a lower waveguide(102) on a substrate(101), an active layer(110) formed on the lower waveguide, and a waveguide on the active layer. A second diffraction grating is formed in a second DFB region which is separated from the first DFB region and includes the lower waveguide, the active layer, and the upper waveguide on the substrate. A phase tuning section is formed between the first DFB region with the first diffraction grating and the second DFB region with the second diffraction grating. A first oscillating wave and a second oscillating wave are generated in the first and second DFB regions by supplying a first current to the first DFB region with the first diffraction grating and a second current to the second DFB region with the second diffraction grating. The phases of the fist and second oscillating waves are controlled by supplying a phase control current to the phase tuning section. The first and second oscillating waves with controlled phases are photo-mixed.

Description

Method for generation of terahertz waves using multi-domain DVF laser devices {Method For Generation Of Terahertz Waves using Distributed Feedback Laser Device}

The present invention relates to a terahertz wave generation method using a multi-domain DFB laser device, and more particularly, to a terahertz using a multi-domain DFB laser device composed of two DFB regions and a phase modulation region including a diffraction grating in each region. It relates to a Hertzian wave generation method.

Functional optical devices that select a specific wavelength in a wavelength division multiplexer (WDM) network, including narrow feedback spectrum (DFB) LD, which is essential for increasing the transmission distance of optical communication, basically filter wavelength using a diffraction grating. As a result, various types of diffraction grating structures have been published and developed.

In the semiconductor-based optical device, wavelength filtering is a light wave propagating in the optical device reflects only a specific wavelength corresponding to the Bragg wavelength by periodic refractive index change and returns to the gain region to oscillate only a specific wavelength. A semiconductor optical device having such a function is manufactured through a process such as semiconductor crystal growth and regrowth, diffraction grating formation, dry / wet etching process, and electrode formation. Recently, in the development of optical communication light source, the advantages of semiconductor optical devices, which are inexpensive, can be mass-produced, and are suitable for small system configurations, and the mode beating of two modes with different wavelengths using a multi-domain DFB structure The research on the development of an external excitation light source for generating, millimeter wave and terahertz wave has been actively conducted.

In particular, much research on terahertz wave generation and detection techniques and imaging systems has been carried out, ranging from radio astronomy observations and spectroscopy applications for detecting organic molecules to terahertz wave imaging systems to be used for in vivo medical imaging operations and security inspections. Because of its application field, it is active in the US, Japan and Europe.

In order to utilize terahertz waves in an imaging system, terahertz wave oscillation characteristics are required, a terahertz wave generating element or system having a variable frequency and having a very narrow bandwidth. Terahertz wave generation methods currently utilized include frequency doubling method, backward wave oscillator, photomixing method, CO ₂ pumped gas laser, quantum cascade laser, and free electron laser. There are a variety of technologies such as (free electron laser).

To generate terahertz waves with continuous oscillation characteristics, variable frequencies, and very narrow bandwidths, two laser beams with different wavelengths are used for photoconductive materials or single travel carrier photodiodes with very short carrier lifetimes. A photomixing method is used in which a terahertz wave corresponding to a wavelength difference between two laser beams is spatially coupled to a uni-travelling-carrier-photodiode (UTC-PD).

The characteristics of the terahertz waves generated when using the photomixing method are determined by the characteristics of the two laser beams and the coherence characteristics of the two laser beams because the terahertz waves are generated by the interference of two laser beams having different wavelengths. . Therefore, in order to realize a low-cost, small-size system that generates continuous and stable terahertz waves with oscillation characteristics, LD that emits two modes having different wavelengths with adjustable wavelength differences and having very stable and mutually coherent characteristics It is very important to realize the compact size by single integration.

Most of the techniques used in the photomixing method use a method of controlling two longitudinal mode intervals of two high-power solid-state lasers or semiconductors so that the frequency difference between the two modes becomes terahertz (THz). For example, US patent (0242287A1) entitled "Optical Terahertz generator / receiver" relates to fabrication of high power terahertz wave sources and receivers by injecting two excitation light sources into the terahertz waveguide. The phase modulation between the wavelengths of the two modes is not possible, which may cause problems in terahertz wave generation efficiency, stability, and size.

Also, IEEE Photonics Technology Letters. (Vol. 7, no. 9, 1995) introduces a related technology for semiconductor laser light sources utilizing two longitudinal modes, entitled "Two-Longitudinal-Mode Laser Diodes." Since the development of multi-wavelength lasers is the main objective and the two modes oscillate in one active region, the frequency difference range of the two modes is very small, the region of the operating injection current is very small and has unstable operating characteristics. It is not effective in terms of terahertz wave generation efficiency.

In addition, since most commercially available DFB LDs use an index-coupled diffraction grating in which the diffraction grating changes the real part of the refractive index to obtain filtering characteristics, the cross-sectional phase, In other words, as the phase of the diffraction grating located in the cross section is changed, the light output characteristic is changed so much that it is difficult to obtain a high single mode oscillation yield.

The present invention has been devised to solve the above problems, and an object of the present invention is to provide a terahertz wave generation method using a multi-domain DFB laser device.

It is still another object of the present invention to provide a DFB laser device capable of increasing terahertz wave generation efficiency using a photomixing method, a manufacturing method thereof, and a terahertz wave generation method.

In addition, an object of the present invention is to change the period difference of the complex-coupled diffraction grating by changing the wavelength, thereby changing each wavelength difference from the very low frequency to the terahertz (THz) region, which is one of the terahertz wave generation methods. It is to provide an external excitation light source technique used in a mixing method.

According to an aspect of the present invention, to achieve the above object, the multi-region Distributed Feedback (DFB) laser device comprises an active layer formed on the substrate; A first DFB region formed in one region of the upper and lower portions of the active layer and including a plurality of first diffraction gratings; A second DFB region formed at a position spaced apart from the first DFB region, the second DFB region including a plurality of second diffraction gratings formed at one of the upper and lower portions of the active layer; And a phase modulation region formed between the first DFB region and the second DFB region.

Preferably, the first DFB region and the second DFB region may include a waveguide formed on the substrate; A first SCH (Separate confinement hetero) layer formed on the waveguide under the active layer; And a second SCH (Separate confinement hetero) layer formed on the active layer. The first diffraction grating and the second diffraction grating have the same period or each different period. At least one of the first diffraction grating and the second diffraction grating is a complex coupled diffraction grating.

According to another aspect of the present invention, a method of manufacturing a multi-region distributed feedback laser device includes a lower waveguide on a substrate, an active layer on the lower waveguide, and an upper waveguide on the active layer. Forming a diffraction grating; Forming a second diffraction grating in a second DFB region including the lower waveguide, the active layer, and the upper waveguide formed on the substrate and positioned at a distance from the first DFB region; And forming a phase modulation region between the first DFB region in which the first diffraction grating is formed and the second DFB region in which the second diffraction grating is formed.

Forming a first diffraction grating in the first DFB region may include forming a cladding layer on the lower waveguide or the upper waveguide; Forming a SiNx layer on the cladding layer; Forming a sinusoidal photoresist on the SiNx layer; Patterning the SiNx layer using the photoresist as a mask; Etching the cladding layer and the lower waveguide or the upper waveguide layer using the patterned SiNx layer; And leaving a first diffraction grating formed in the first DFB region.

Forming a second diffraction grating in the second DFB region may include forming a cladding layer on the lower waveguide or the upper waveguide; Forming a SiNx layer on the cladding layer; Forming a sinusoidal photoresist on the SiNx layer; Patterning the SiNx layer using the photoresist as a mask; Etching the cladding layer and the lower waveguide or the upper waveguide layer using the patterned SiNx layer; And leaving a second diffraction grating formed in the second DFB region. Doping p-type ions into the first and second diffraction gratings. In the step of patterning the SiNx layer using the photoresist as a mask, a holography method or an electron beam lithography method is used.

The etching of the lower waveguide or the upper waveguide uses a holography method or an electron beam lithography method. At least one of the first diffraction grating and the second diffraction grating is a complex coupled diffraction grating. Forming the phase modulation region includes removing the upper waveguide and the active layer. Removing the active layer uses at least one of a lithography method and an etching method.

According to another aspect of the invention, the method for generating a terahertz wave of the present invention is a multi-domain DFB laser device manufactured according to the method for producing a multi-domain DFB laser device of any one of claims 5 to 7. It is used as an external excitation light source.

According to the foregoing description, the present invention has two modes of different wavelengths of continuous oscillation with highly stable and mutually coherent characteristics emitted from a multi-domain complex-coupled DFB laser composed of two complex-coupled DFB regions and a phase modulation region. Can be used as an external excitation light source to develop low cost and small terahertz wave sources and receivers.

In addition, the present invention can provide an external excitation light source technology that is relatively easy to fabricate and capable of producing high power terahertz waves that are small, stable at room temperature and continuously oscillate.

The present invention continuously emits two modes with different coherent characteristics and different wavelengths, and changes the period difference of the complex-coupled diffraction grating, thereby reducing the frequency difference between the two modes emitted by the multi-domain DFB laser at a very low frequency. You can change it to the area.

According to the present invention, when the oscillation mode is not placed in the forbidden band of another DFB region, the oscillated mode proceeds without large reflection to another DFB region, so that the interaction between the two modes occurs largely and thus a multi-domain DFB laser having an IC diffraction grating. In contrast, a very large modulation index can be obtained, and the terahertz wave generation efficiency is very high when generating terahertz waves using a photomixing method.

Hereinafter, the most preferred embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily implement the technical idea of the present invention. .

1A to 1K are process flowcharts sequentially illustrating a manufacturing process of a multi-region distributed feedback laser device LD according to the present invention.

Referring to FIG. 1A, to manufacture a multi-region DFB LD, first, a lower waveguide 102 on which a first diffraction grating layer is to be formed is formed on a substrate 101. The substrate 101 is formed of an n-type InP semiconductor substrate, and the lower waveguide 102 forms InGaAsP (λ _PL = 1.3 μm) in a thickness of 100 kV to 500 kV. An n-type InP layer 103 is formed as a cladding layer on the lower waveguide 102. The n-type InP layer 103 is formed in a thickness range of greater than 0 and less than or equal to 200 mm 3, and most commonly formed in a thickness of about 100 mm 3. The SiNx layer 104 is formed on the n-type InP layer 103 for fabricating the first diffraction grating layer. SiNx layer 104 is deposited to a thickness of about 300 ~ 500Å.

Referring to FIG. 1B, a photoresist material layer is applied on the SiNx layer 104, and the photoresist material layer is formed of a plurality of photoresist 105 in sinusoidal form through a holography system. In the present embodiment, to form the photoresist 105, a holography system composed of an Ar ion laser is used. At this time, the period of the sinusoidal photoresist 105 is determined by the angle of the two beams of the Ar ion laser used. In general, in the case of DFB laser device, the structure and material composition of the active layer to be formed are related, and the oscillation wavelength of the laser device to be manufactured is made in the vicinity of 1.55㎛ which has the smallest propagation loss of the transmission path (optical fiber) of the optical communication system. In order to make it clear, it forms and uses about 240 nm period.

Referring to FIG. 1C, in the next process, the SiNx layer 104 is first etched using the photoresist 105 as an etch barrier. In order to pattern the SiNx layer 104 in the form of a mask, it is preferable to etch the SiNx layer 104 using magnetically enhanced reactive ion etching (MERIE).

Next, referring to FIG. 1D, layers formed under the SiNx layer 104 are etched using a non-selective etchant using the SiNx layer 104 patterned in the form of a mask. When the etching process is performed, an upper portion of the n-type InP layer 103, the lower waveguide 102, and the semiconductor substrate 101 is etched. Part of the upper surface of the semiconductor substrate 101 is etched to provide regrowth and diffraction grating characteristics. The n-type InP layer 103 and the lower waveguide 102 are used to transfer the diffraction gratings to the grown InGaAsP layer. Etch 100 ~ 200Å more than the thickness of InGaAsP layer.

Referring to FIG. 1E, in the next process, the multi-region DFB LD or a special-purpose optical element of the pattern of the lower waveguide 102 formed through the etching process, that is, to be used as a diffraction grating in the entire region above the substrate 101. For fabrication, a pattern formed on one area of the upper portion of the substrate 101 is left and the remaining pattern area is removed. A lithography process is performed to remove portions of the lower waveguide pattern 102 that are not used as the first diffraction grating. When a portion of the pattern is removed through the lithography process, only the first diffraction grating is formed in one region of the substrate 101. There is a waveguide pattern to be used.

Referring to FIG. 1F, an n-type InP layer 107 covering the first diffraction grating 102 is formed on the substrate 101 on which the first diffraction grating 102 (the lower optical waveguide) is formed in one region of the substrate 101. Is formed. The n-type InP layer 107 is deposited and planarized by metal organic chemical vapor deposition (MOCVD). In the present embodiment, since the n-type InP layer 107 is the same material as the semiconductor substrate 101, the n-type InP may be omitted because it is incorporated in the substrate 101 and can be regarded as the same layer. In the case where the planarization operation is artificially performed by doping the layer 107 or the like, the present disclosure may be distinguished from the substrate 101 as a separate layer.

Referring to FIG. 1G, in the next step, an InGaAsP layer 108, which is a waveguide layer of an optical element, is formed on the n-type InP 107 layer. The InGaAsP layer 108 may be grown to a thickness of 0.1 μm to 0.3 μm, and various growth wavelengths λ _PL may be controlled by controlling growth conditions. In the present embodiment, a wavelength of 1.2 μm to 1.3 μm is used. The first SCH layer 109a, the active layer 110, and the second SCH layer 109b are deposited on the InGaAsP layer 108. Claim 1 SCH layer (109a) and a 2 SCH layer (109b) is an InGaAsP of about each of the wavelength (λ _PL) is formed from a 1.3㎛ 0.1㎛ thickness. The active layer 110 is a bulk layer composed only of InGaAsP with multi-quantum wells (MQW) or InGaAsP (λ _PL = 1.45 to 1.55 μm) having a well shape, and the wavelength of the active layer 110 is the oscillation of the fabricated DFB laser device. Related to the wavelength, which can vary in accordance with the desired oscillation wavelength value, in the present embodiment has a wavelength of 1.45 ~ 1.55㎛.

Next, the p-type cladding layer 111 is formed on the second SCH layer 109b. The p-type cladding layer 111 is deposited as a p-type InP layer with a thickness of about 0.1 μm. The (108) to (111) layers have a structure that can be used as an active layer. Next, an undoped or p-type InGaAsP layer (λ _PL = 1.3 μm) 112 is formed on the clad layer 111 to a thickness of 100 μs to 500 μs, and the p-type InGaAsP layer 112 is formed. ), The same p-type InP layer 113 as the clad layer 111 is formed to have a thickness of 100 kV. Next, a SiNx layer 114 for fabricating a second diffraction grating layer is formed on the p-type InP layer 113. The SiNx layer 114 is a layer for fabricating the second diffraction grating layer. The SiNx layer 114 is deposited to have a thickness of about 300 to 500 mV. Photoresist 115 is formed.

Next, FIG. 1H will be described with reference to FIGS. 1C to 1E described above. First, the SiNx layer 114 is etched using the photoresist 115 as an etch barrier. At this time, by etching using magnetically enhanced reactive ion etching (MERIE), it is possible to pattern the SiNx layer 114 in the form of a mask. In the next process, the layer formed under the SiNx layer 114 is etched using a non-selective etching solution using the SiNx layer 114 patterned in the form of a mask. When the etching process is performed, portions of the upper surfaces of the n-type InP layer 113, the p-type InGaAsP layer 112, and the clad layer 111 are etched. Part of the upper surface of the clad layer 111 is etched to provide regrowth and diffraction grating characteristics. In the next step, the remaining diffraction gratings are removed, leaving only one area of the diffraction gratings in order to fabricate the multi-region DFB LD or the optical device for a special use among the formed total diffraction gratings. In order to remove some of the diffraction gratings, when the lithography process is performed, a second diffraction pattern formed of a p-type InGaAsP layer 112 (second diffraction grating layer) patterned only in one region on the clad layer 111 is disclosed as shown in FIG. 1E. There is a grid.

Referring to FIG. 1I, the next step forms a phase tuning region (P) of the multi-domain DFB LD. In the case of the multi-region DFB LD, since the phase modulation region P is a region for controlling the phase of the light wave by current injection, it is advantageous to remove the cladding layer 111 from the active layer 110 to the characteristics of the optical device. In order to remove the active layer 110, a lithography method and an etching method are used. Meanwhile, in the present exemplary embodiment, although the first SCH layer 109a and the InGaAsP layer 108 are formed as the waveguide layer under the active layer 110, the InGaAsP layer 108 may be used to leave only the waveguide layer in the phase modulation region P. ) And an InP layer may be inserted between the SCH layer 109a and used as an etch stop layer.

After the formation of the first and second diffraction grating layers 102 and 112 and the phase modulation region P is completed, referring to FIG. 1J, the p-type cladding layer 116 formed of p-type InP on the cladding layer 111 is formed. Is deposited. The p-type InP layer 116 is grown and planarized by an organometallic chemical vapor deposition method. In the present embodiment, since the p-type InP layer 116 is the same material as the clad layer 111, it may be incorporated into a substrate and considered as the same layer. Subsequently, in order to grow a structure for current confinement, after forming a waveguide for a resonator, to fabricate a planar buried hetero structure (PBH) type optical device, p-InP, n-InP, and p-InP, which are current blocking layers, Regrowth is sequentially performed using MOCVD on the substrate on which the waveguide is formed. In the next step, an InGaAs layer 117 is formed on the p-type cladding layer 116 to increase electrical conductivity.

In the next step, referring to FIG. 1K, after the silicon nitride film 118 is deposited on the InGaAs layer 117, the active layer 110 is injected into the active layer 110 only by lithography and etching. One region of the InGaAs layer 117 is etched to electrically short the non-formed portion and the current of the other portion is blocked by the silicon nitride film 118.

2A to 2C are first to third embodiments of the multi-domain DFB laser device according to the present invention. Referring to FIG. 2A, the diffraction gratings 102 and 112 are formed in the lower partial region of the active layer 110 and the upper partial region of the active layer 110, respectively. Referring to FIG. 2B, a phase The diffraction gratings are formed in the upper region of the active layer except for the modulation region. Referring to FIG. 2C, the diffraction gratings are formed in the lower region of the active layer except for the phase modulation region.

Although the first embodiment disclosed in FIG. 2A shows a DFB LD manufactured using the manufacturing process of FIGS. 1A to 1K as it is, the embodiments shown in FIGS. 2B and 2C are formed using one diffraction grating formation process. can do. In addition, the upper diffraction grating may be formed in the first DFB region and the lower diffraction grating may be formed in the second DFB region. The diffraction gratings formed in each region may be formed of diffraction gratings having the same characteristics or diffraction gratings having different characteristics. For example, each of the diffraction gratings may be all formed of an IP complex coupled diffraction grating, and only one of them may be formed of the IP complex coupled diffraction grating.

3A and 3B are diagrams showing reflection spectra of respective DFB regions of a multi-domain DFB laser device having an in-phase (IP) diffraction grating according to the present invention. Specifically, FIGS. 3A and 3B are reflection spectra in the first and second DFB regions, each having an In-phase (IP) complex diffraction grating above the threshold current.

FIG. 3A illustrates a case where the forbidden bandwidths of the reflection spectra overlap each other (Δλ _B <Δ), and FIG. 3B illustrates a spectrum when the forbidden bandwidths of the reflectance spectra do not overlap each other (Δλ _B > Δ). 3A and 3B, the horizontal axis represents wavelength and the vertical axis represents reflectivity. When the lattice period of the second DFB region is set to be larger than the lattice period of the first DFB region, the Bragg wavelength of the second DFB region is set to the first wavelength. It is larger than the Bragg wavelength in the DFB region. Where? Is the forbidden bandwidth of the DFB region, and Δλ _B represents the Bragg wavelength difference of the old DFB region. In the CC DFB region having the IP complex coupling diffraction grating, the +1 mode and the +2 mode, which are long wavelength modes, oscillate.

Therefore, unlike the case of using the IC (index coupled) DFB structure, even when Bragg wavelength difference (diffraction grating period difference) is larger than the forbidden bandwidth, +1 mode and +2 mode are oscillated in each CC (complex coupled) DFB region. . Therefore, in each CC DFB region, a stable mode oscillates and emits two stable modes as compared with the case of using the IC DFB structure, and two modes due to mode hopping between the short wavelength mode and the long wavelength mode will occur. No abrupt change in the wavelength difference of the mode will occur.

In the case of a multi-domain DFB laser using the CC DFB structure, the frequency (frequency due to the wavelength difference) generated by the mode beating in the +1 mode and the +2 mode can be expressed by the following equation.

f = cΔλ _B / λ ²

4A to 4F are characteristic graphs when the diffraction grating of each of the DFB regions according to the present invention has an IP complex-coupled structure.

4A to 4F are graphs according to Δλ _B , and FIG. 4A is a frequency difference between two modes of oscillation, FIG. 4B is a wavelength of +1 mode and +2 mode, and FIGS. 4C and 4D. Denotes the average output power at the second DFB region side and the modulation index of the output power and output power at the +1 mode and the +2 mode, respectively, and FIGS. 4E and 4F are the average output power at the first DFB region side and the +1 mode, respectively. Output power in +2 mode and modulation index of output power are shown. Each graph shown in FIG. 4 shows a modulation index calculation result for output power of an external excitation light source, which is one of important factors for determining generation efficiency when generating terahertz waves using a photomixing method.

According to each graph, it can be confirmed that the modulation index characteristics are good, thereby confirming that terahertz wave generation efficiency is good. In particular, the graphs of FIG. 4 show that by varying the period difference of the complex-coupled diffraction grating, the wavelength difference of the two modes occurring in a multi-domain DFB laser with an IP (AP) diffraction grating can be varied from very low frequency to about 3 THz. Indicates.

Although the technical spirit of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will appreciate that various embodiments are possible within the scope of the technical idea of the present invention.

1A to 1K are process flowcharts sequentially showing a manufacturing process of a multi-domain DFB laser device according to the present invention.

2A to 2C are first to third embodiments of the multi-domain DFB laser device according to the present invention.

3A and 3B show reflection spectra of each DFB region of a multi-domain DFB laser device having an in-phase (IP) diffraction grating according to the present invention.

4A to 4F are characteristic graphs when the diffraction grating of each of the DFB regions according to the present invention has an IP complex-coupled structure.

** Explanation of symbols on the main parts of the drawing **

101: substrate 102: lower waveguide (first diffraction grating)

103: n-type InP layer 104: SiNx layer

105: photoresist 107: n-type InP layer

108: InGaAsP layer 109a: first SCH layer

109b: second SCH layer 110: active layer

111: p-type cladding layer 112: p-type InGaAsP layer

113: p-type InP layer 114: SiNx layer

115: photoresist 116: p-type InP layer

117: InGaAs layer 118: silicon nitride film

Claims (9)

Forming a first diffraction grating in a first DFB region comprising a lower waveguide on a substrate, an active layer over the lower waveguide, and an upper waveguide over the active layer; Forming a second diffraction grating in a second DFB region including the lower waveguide, the active layer, and the upper waveguide formed on the substrate and positioned at a distance from the first DFB region; Forming a phase modulation region between the first DFB region in which the first diffraction grating is formed and the second DFB region in which the second diffraction grating is formed; The first current is supplied to the first DFB region in which the first diffraction grating is formed, and the second current is supplied to the second DFB region in which the second diffraction defect is formed, thereby providing a first current in the first DFB region and the second DFB region. Generating a first oscillation wave and a second oscillation wave; Supplying a phase adjustment current to the phase modulation region to adjust phases of the first oscillation wave and the second oscillation wave; and Photomixing the first oscillation wave and the second oscillation wave whose phase is adjusted; Including, wherein the oscillation wavelength of the first oscillation wave is reduced and the oscillation wavelength of the second oscillation wave is increased in proportion to the Bragg wavelength difference of the first oscillation wave and the second oscillation wave Method for generating a terahertzpa characterized in that. The method of claim 1, Forming a first diffraction grating in the first DFB region, Forming a cladding layer on the lower waveguide or the upper waveguide; Forming a SiNx layer on the cladding layer; Forming a sinusoidal photoresist on the SiNx layer; Patterning the SiNx layer using the photoresist as a mask; Etching the cladding layer and the lower waveguide or the upper waveguide layer using the patterned SiNx layer; And Leaving a first diffraction grating formed in the first DFB region How to generate a terahertza containing. The method of claim 1, Forming a second diffraction grating in the second DFB region, Forming a cladding layer on the lower waveguide or the upper waveguide; Forming a SiNx layer on the cladding layer; Forming a sinusoidal photoresist on the SiNx layer; Patterning the SiNx layer using the photoresist as a mask; Etching the cladding layer and the lower waveguide or the upper waveguide layer using the patterned SiNx layer; And Leaving a second diffraction grating formed in the second DFB region How to generate a terahertza containing. The method according to claim 2 or 3, And doping p-type ions into the first and second diffraction gratings. The method according to claim 2 or 3, Patterning the SiNx layer using the photoresist as a mask to generate terahertz waves using a holography method or an electron beam lithography method. The method according to claim 2 or 3, Etching the lower waveguide or the upper waveguide comprises generating a terahertz wave using a holography method or an electron beam lithography method. The method according to claim 2 or 3, And at least one of the first and second diffraction gratings generates a terahertz wave, which is a complex coupled diffraction grating. The method of claim 1, Forming the phase modulation region comprises removing the upper waveguide and the active layer. The method of claim 8, And removing the active layer comprises using at least one of a lithographic method and an etching method.

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