TWI680619B - Distributed feedback semiconductor laser device - Google Patents

Abstract

A distributed feedback semiconductor laser device includes an active layer, a first grating layer, and a second grating layer. The first grating layer includes a first grating structure having a first grating period. The second grating layer includes a second grating structure having a second grating period, wherein the second grating period is substantially different from the first grating period. The active layer, the first grating layer and the second grating layer are stacked on top of each other, and the equivalent grating period of the distributed feedback semiconductor laser device is (2 × P1 × P2) / (P1 + P2), where P1 and P2 These are the first grating period and the second grating period, respectively.

Description

Distributed feedback semiconductor laser device

The present invention relates to a semiconductor laser device, and more particularly to a distributed feedback (DFB) semiconductor laser device with a single wavelength light output.

Semiconductor lasers mainly include Fabry-Perot (FP) lasers, distributed feedback lasers, and vertical cavity surface emitting lasers (VCSELs). For distributed feedback lasers, its wavelength stability and side mode suppression ratio (SMSR) are the key factors for production yield. The main cause of laser failure is the use of a distributed symmetrical grating structure. The feedback laser causes the wavelength of the laser to emit light not at the Bragg wavelength corresponding to the grating structure, but to emit light at both ends of its Bragg wavelength. Forbidden band edges to form unstable dual-wavelength light output. Although phase shift gratings can be fabricated using electron beam lithography to improve wavelength stability and side-mode suppression ratio, the production cost and time of relatively distributed feedback lasers have also increased significantly.

The object of the present invention is to provide a distributed feedback semiconductor laser device, which has single-mode output characteristics, that is, the difference between the energy of the primary mode and the energy of the secondary mode is at least 30dB, and has high wavelength stability, high side mode suppression ratio, and Improved space cavitation effect during operation. In addition, the grating structure in a distributed feedback semiconductor laser device can be defined through laser interference lithography and wet etching. Therefore, compared with the electron beam lithography technology, the manufacturing cost and time can be effectively reduced.

According to the above objective, the present invention provides a distributed feedback semiconductor laser device, which includes an active layer, a first grating layer, and a second grating layer. The first grating layer includes a first grating structure having a first grating period, and the second grating layer includes a second grating structure having a second grating period, wherein the first grating period is substantially different from the second grating period. The active layer, the first grating layer and the second grating layer are stacked on top of each other, and the equivalent grating period of the distributed feedback semiconductor laser device is (2 × P1 × P2) / (P1 + P2), where P1 and P2 These are the first grating period and the second grating period, respectively.

According to an embodiment of the present invention, the first grating layer and the second grating layer are located on the same side of the active layer.

According to another embodiment of the present invention, the second grating layer is directly stacked on the first grating layer.

According to another embodiment of the present invention, the first grating layer and the second grating layer are located on opposite sides of the active layer, respectively.

According to another embodiment of the present invention, a gap between the first grating period and the second grating period is substantially lower than 1 nanometer (nm).

According to another embodiment of the present invention, a filling factor of the first grating structure and the second grating structure is about 0.4 to 0.5.

According to another embodiment of the present invention, when the light advances in the active layer, the optical confinement factor for the first grating structure and the second grating structure is substantially the same.

According to the above object, the present invention further provides a distributed feedback semiconductor laser device including an active layer and a grating layer including a grating structure. The active layer and the grating layer are stacked on top of each other, and the grating structure has periodic height or depth changes.

According to an embodiment of the present invention, the height change and the depth change of the grating structure correspond to waveforms after superposition of two different sine functions.

According to yet another embodiment of the present invention, the height of the microstructure, the depth of the groove and the height and depth change period of the microstructure in the grating structure are adjusted by the exposure time or dose of the holographic interference lithography process.

100, 200, 300, 400‧‧‧ Distributed feedback semiconductor laser device

110, 210, 310, 410‧‧‧ active layer

111, 211, 311‧‧‧ multiple quantum well formations

112, 212, 312, ‧‧‧ separation and limited heterogeneous structure

113, 213, 313, ‧‧‧, separated confined heterogeneous structures

120, 220, 320‧‧‧‧ First grating layer

121, 221, 321‧‧‧ first grating structure

122, 132, 222, 232, 322, 332‧‧‧ coating

130, 230, 330‧‧‧ Second grating layer

131, 231, 331‧‧‧Second grating structure

140, 240, 340‧‧‧ buffer layer

150, 250, 350‧‧‧ substrate

160, 260, 360‧‧‧ coating

170, 270, 370‧‧‧ contact layer

180, 280, 380‧‧‧ passivation layer

192, 292, 392‧‧‧ upper electrode layer

194, 294, 394‧‧‧ lower electrode layer

420‧‧‧Grating layer

421, 421 ’, 421” ‧‧‧ grating structure

P _L ‧‧‧Long cycle

P _S ‧‧‧short cycle

P1, P2‧‧‧cycle

W1, W2‧‧‧ String

For a more complete understanding of the embodiment and its advantages, reference is now made to the following description in conjunction with the drawings, in which: [FIG. 1] is a schematic perspective view of a distributed feedback semiconductor laser device according to an embodiment of the present invention; [FIG. 2] [Fig. 1] is a sectional view of a partial structure of a distributed feedback semiconductor laser device; [Fig. 3] is a schematic diagram of sine waves of two different periods and their added waveforms; [Fig. 4] shows a light transmission and reflection spectrum equivalent to the first grating structure and the second grating structure in a distributed feedback semiconductor laser device according to an embodiment of the present invention; [Fig. 5] shows the basis Luminous power characteristics of the lasers generated by the distributed feedback semiconductor laser device according to the embodiment of the present invention at different temperatures and different operating currents; [FIG. 6] shows the results generated by the distributed feedback semiconductor laser device according to the embodiment of the present invention. Luminous spectrum characteristics of laser light at an ambient temperature of 20 ° C; [Fig. 7] is caused by a change in operating current of the laser light generated by a distributed feedback semiconductor laser device according to an embodiment of the present invention at an ambient temperature of 20 ° C Measurement results of changes in wavelength and side mode suppression ratio; [Fig. 8] shows the wavelengths and wavelengths caused by ambient temperature changes of the laser light generated by the distributed feedback semiconductor laser device according to the embodiment of the present invention at an operating current of 60 mA. Measurement results of changes in the side mode suppression ratio; [Fig. 9] shows the laser light generated by the distributed feedback semiconductor laser device according to the embodiment of the present invention at different operating voltages; The corresponding measurement results of the corresponding electrical / optical response (E / O response) S21; [Figure 10] shows the corresponding laser light generated by a distributed feedback semiconductor laser device according to an embodiment of the present invention at an operating current of 60 mA. Bit error rate (BER) and optical eye diagram; [Fig. 11] is a perspective view of a distributed feedback semiconductor laser device according to another embodiment of the present invention; [Fig. 12] is the distribution of [Fig. 11] Partial structure cross-sectional view of a feedback semiconductor laser device; [FIG. 13] is a perspective view of a distributed feedback semiconductor laser device according to another embodiment of the present invention; [FIG. 14] is a partial cross-sectional view of the distributed feedback semiconductor laser device of FIG. 13; [FIG. 15] This is a cross-sectional view of a partial structure of a distributed feedback semiconductor laser device according to another embodiment of the present invention; [FIG. 16A] is a waveform diagram of laser light generated by the distributed feedback semiconductor laser device of FIG. 15; and [FIG. 16B] ] To [Fig. 16D] are different examples of the grating layer of [Fig. 15].

Embodiments of the invention are discussed in detail below. It is understood, however, that the embodiments provide many applicable concepts that can be embodied in a wide variety of specific content. The embodiments discussed and disclosed are for illustration only and are not intended to limit the scope of the invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of patent applications. Unless otherwise limited, the singular forms "a" or "the" can also be used to indicate the plural form. In addition, the term “spatial relativity” is used to explain the different orientations of the components during use or operation, and is not limited to the directions shown in the drawings. Elements can also be oriented in other ways (rotated 90 degrees or in other directions), and the spatially relative description used here can be interpreted in the same way.

For simplicity and clarity of illustration, element symbols and / or letters may be reused in various embodiments herein, but this does not indicate a causal relationship between the various embodiments and / or configurations discussed.

In addition, spatial relative terms may be used in this article, such as "over", "on", "under", "below", etc., to facilitate the illustration as shown in the figure Draw the relationship between one element or feature and another element or feature.

In order to facilitate understanding of the content of the present case, the drawings may only show a part of the complete structure, but it is not intended to limit the scope of the present invention in any way. Those with ordinary knowledge in the technical field to which the present invention pertains can directly derive the complete structure from the part of the structure shown in the drawings according to the content of this document.

FIG. 1 is a schematic perspective view of a distributed feedback semiconductor laser device 100 according to an embodiment of the present invention. In the distributed feedback semiconductor laser device 100, the active layer 110 includes a multiple quantum well (MQW) layer structure 111 and a separate confinement heterostructure (SCH) layer 112, 113. The multiple quantum well layer structure 111 may include staggered stacks of n quantum well layers and (n-1) or (n + 1) barrier layers, wherein the quantum well layer may be composed of indium gallium arsenide (InGaAs). The barrier layer may be made of indium aluminum gallium arsenide (InAlGaAs). The thickness of each quantum well layer may be about 5 nm, and the thickness of each barrier layer may be about 8.5 nm. The separated confined heterogeneous structure layers 112 and 113 are respectively located on the upper and lower sides of the multiple quantum well layer structure 111. The confined confined heterogeneous structure layer 112 may include an In _0.53 Al _x Ga _(0.47-x) As layer with a thickness of 50 nm, where x is 0.36 to 0.44, and a P-type In _0.52 Al _0.48 As layer with a thickness of 50 nm; the separated confined heterostructure layer 113 may include an In _0.53 Al _x Ga _(0.47-x) As layer with a thickness of 50 nm, where x is 0.36 To 0.44, and an N-type In _0.52 Al _0.48 As layer with a thickness of 50 nm.

Please refer to FIG. 2 together, which is a partial cross-sectional view of a distributed feedback semiconductor laser device 100. As shown in FIGS. 1 and 2, the first grating layer 120 and the second grating layer 130 are sequentially stacked over the active layer 110. The first grating layer 120 has a first grating structure 121 and a coating layer 122, and the second grating layer 130 has a second grating structure 131 and a coating layer 132. The grating period P1 of the first grating structure 121 and the grating period P2 of the second grating structure 131 are different. In the embodiment shown in FIG. 2, the grating period P1 of the first grating structure 121 is greater than the grating period P2 of the second grating structure 131. In other embodiments, the grating period P1 of the first grating structure 121 may be smaller than the grating period P2 of the second grating structure 131. The equivalent grating period of the combination of the first grating structure 121 and the second grating structure 131 is (2 × P1 × P2) / (P1 + P2). The coating layer 122 covers the first grating structure 121 and fills the space in the first grating structure 121, and the coating layer 132 covers the second grating structure 131 and fills the space in the second grating structure 131. The refractive indexes of the first grating structure 121 and the second grating structure 131 may be greater than the refractive indexes of the coating layers 122 and 132, respectively.

The gap between the grating period P1 of the first grating structure 121 and the grating period P2 of the second grating structure 131 may be less than 1 nm to ensure the single-mode output characteristics of the distributed feedback semiconductor laser device 100. In addition, the filling factor of the first grating structure 121 and the second grating structure 131 factor) may be about 0.4 to 0.5 to increase the intensity of optical coupling between the first grating structure 121 and the second grating structure 131.

The material of the first grating structure 121 and the second grating structure 131 may be P-type indium gallium arsenide phosphide (InGaAsP), and the material of the coating layers 122 and 132 may be P-type indium phosphide; InP). In other embodiments, the first grating structure 121, the second grating structure 131, and the coatings 122, 132 may be composed of other materials. For example, the first grating structure 121 and the second grating structure 131 may be made of P-type aluminum indium gallium phosphide (AlInGaP), and the coating layers 122 and 132 may be made of P-type gallium arsenide (GaAs). ) Structure. The thicknesses of the first grating structure 121 and the second grating structure 131 may be the same or different, and the materials constituting the first grating structure 121 and the second grating structure 131 may be the same or different.

The buffer layer 140 is located under the active layer 110 and may be composed of N-type indium phosphide. The substrate 150 is located under the buffer layer 140, and has a thickness of about 100 μm. The substrate 150 can be made of indium phosphide (InP). The cladding layer 160 is located above the second grating layer 130. The thickness of the cladding layer 160 may be about 2 μm, and the cladding layer 160 may be made of P-type indium phosphide.

In some embodiments, between the active layer 110 and the first grating layer 120, a P-type InP layer having a thickness of about 10 nm, a P-type InGaAsP layer having a thickness of about 15 nm, and a P-type layer having a thickness of about 25 nm may be sequentially included. type InP layer, and between the active layer 110 and the buffer layer 140 may comprise a thickness of about 10nm N-type _{in 0.53 Al x Ga (0.47-} x) as layer, where x is from 0.36 to 0.44.

Elements above the cladding layer 160 include a contact layer 170, a passivation layer 180, and an upper electrode layer 192, and elements below the substrate 150 include a lower electrode layer 194. As shown in FIG. 1, the contact layer 170, the passivation layer 180, and the upper electrode layer 192 constitute a ridge waveguide structure. The contact layer 170 may be composed of InGaAs and InGaAsP with a high doping concentration, the passivation layer 180 may be composed of silicon oxide, and the upper electrode layer 192 and the lower electrode layer 194 may be composed of titanium, platinum, gold, or other suitable metals.

In addition, according to application requirements, a high-reflection film and an anti-reflection film may be plated on both ends of the laser resonant cavity constituting the distributed feedback semiconductor laser device 100, respectively. Both of the reflective film and the high-reflection film are plated with a high-reflection film, the anti-reflection film is plated, or neither is plated.

Please refer to FIG. 2 again. In the distributed feedback semiconductor laser device 100, the relative positions of the first grating structure 121 and the second grating structure 131 with respect to the laser cavity may be aligned or misaligned. That is, the first grating structure 121 and the second grating structure 131 located on either end surface of the distributed resonant semiconductor laser device 100 constituting the laser resonant cavity may be completely aligned, completely misaligned, or between the two. between.

An example of a manufacturing method of the distributed feedback semiconductor laser device 100 is as follows. First, a substrate 150 is provided, and then a buffer layer 140 and an active layer 110 are sequentially formed on a plane of the substrate 150, where the active layer 110 includes a lower separated confined heterogeneous structure 112 and a multiple quantum well layer structure that are sequentially stacked from bottom to top. 111 and 113 separated on the confined heterogeneous structure. After that, a first grating layer 120 and a second grating layer 130 are sequentially formed on the active layer 110. Examples of the method for forming the first grating layer 120 and the second grating layer 130 are as follows. First, a grating material layer is deposited on the active layer 110, and then a laser interference lithography process and wet etching are performed on the grating material layer to form a first grating structure 121, and then a coating is formed on the first grating structure 121. 122. In other embodiments, a partial coating layer 122 and a grating material layer may be formed on the active layer 110, and then a laser interference lithography process and wet etching are performed on the grating material layer to form a first grating. Structure 121, and then another coating layer 122 is formed on the first grating structure 121. After the first grating layer 120 is completed, another grating material layer is deposited on the first grating layer 120, and then a laser interference lithography process and wet etching are performed on the grating material layer again to form a second grating structure 131. A coating layer 132 is then formed on the second grating structure 131.

Next, a cladding layer 160 and a contact layer 170 are formed on the second grating layer 130, and a ridge region is defined. Thereafter, a passivation layer 180 and an upper electrode layer 192 are sequentially formed on the cladding layer 160 and the contact layer 170 to form a ridge waveguide structure on the distributed feedback semiconductor laser device 100, and finally on another plane of the substrate 150 The lower electrode layer 194 is formed on it.

FIG. 3 is a schematic diagram of sine waves of two different periods and their added waveforms, where the sine wave W1 is the cross-sectional profile of the first grating layer 120 and the sine wave W2 is the cross-sectional profile of the second grating layer 130. As shown, the sine wave W1 3, W2 are periodic sine wave, and the period, respectively P ₁ and P _2. The composite waves W1 + W2 of the sine waves W1 and W2 have a periodic waveform of an envelope, and the short and long periods thereof are P _S and P _{L, respectively} . Composite wave W1 + W2 of the short period and long period P _S P _L respectively (2 × P1 × P2) / (P1 + P2) and (2 × P1 × P2) / | P1-P2 |. If the periods of the sine waves W1 and W2 are 202.16 nm and 201.84 nm, respectively, the short period P _S and the long period P _L are about 202 nm and 250 μm, respectively, which correspond to the equivalent grating period and the lightning of the feedback semiconductor laser device 100, respectively. Radiation cavity length. Equivalent based on grating period P _S emission wavelength [lambda] of the relationship λ = 2n _eff P _S, the distribution of laser beam 100 to produce a feedback semiconductor laser device of a wavelength [lambda] may be equivalent and the equivalent refractive index n _eff grating period P _S To decide.

Please return to FIG. 2. The thickness T1 of the first grating structure 121 and the thickness T2 of the second grating structure 131 determine the optical confinement factor. When the grating periods of the first grating structure 121 and the second grating structure 131 are 202.16 nm and 201.84 nm, respectively, if the thickness T1 of the first grating structure 121 and the thickness T2 of the second grating structure 131 are both 15 nm, the first grating structure 121 The light confinement factors of 121 and the second grating structure 131 are approximately 0.0154 and 0.0087, respectively. The difference in the limitation factors of the first grating structure 121 and the second grating structure 131 will affect the optical coupling strength of the first grating structure 121 and the second grating structure 131. If the thickness T2 of the second grating structure 131 is changed to 27 nm, the light confinement factors of the first grating structure 121 and the second grating structure 131 become approximately 0.0158 and 0.0158, respectively. Since the light confinement factors of the first grating structure 121 and the second grating structure 131 become substantially the same, the two gratings have the same optical coupling intensity. In addition, the light coupling intensity of the first grating structure 121 and the second grating structure 131 is about 42.8 cm ^-1 .

FIG. 4 is a measurement result of light transmission and reflection spectrums equivalently generated by the first grating structure 121 and the second grating structure 131 in the distributed feedback semiconductor laser device 100. It can be seen from FIG. 4 that the transmission and reflection spectrum has a significant change in the transmission and reflection optical intensity at a wavelength of about 1.31 μm (ie, the Bragg wavelength of 1310 nm), while the transmission and reflection optical intensity at other wavelengths is Is roughly unchanged. In addition, if the phase difference between the first grating structure 121 and the second grating structure 131 is changed, for example, the phase difference between the first grating structure 121 and the second grating structure 131 is changed from 0 degrees to 90 degrees, the generated transmission and reflection spectrum It is still similar to the transmission and reflection spectrum of FIG. 4. Therefore, in the distributed feedback semiconductor laser device 100, the first grating structure 121 and the second grating structure 131 do not need to be accurately aligned with each other. It can be known from the above that the light transmission and reflection spectrums equivalently generated by the first grating structure 121 and the second grating structure 131 have the spectral response characteristics of a phase shift grating.

FIG. 5 shows the measurement results of the luminous power of the distributed feedback laser light generated by the distributed feedback semiconductor laser device 100 at different temperatures and different operating currents. By analyzing the measurement results in FIG. 5, it can be known that the critical current and characteristic temperature of the distributed feedback semiconductor laser device 100 are about 13 mA and 78 K, respectively, and can have an output power of more than 10 mW at an ambient temperature of 60 ° C. .

FIG. 6 shows the emission spectrum characteristics of the distributed feedback laser light generated by the distributed feedback semiconductor laser device 100 at an ambient temperature of 20 ° C. The measurement results in FIG. 6 show that the wavelength of the laser light generated by the distributed feedback semiconductor laser device 100 does not fall on the stopband edge, but falls near the Bragg wavelength of 1310 nm, which is equivalent to a quarter. Laser characteristics of wavelength phase shift.

Figure 7 is the measurement result of the wavelength change and the side mode suppression ratio caused by the operating current change at an ambient temperature of 20 ° C, and Figure 8 is the wavelength change and the side mode suppression caused by the ambient temperature change at the operating current of 60 mA Ratio of measurement results. Figures 7 and 8 show that the operating current is 20mA to Under the conditions of 130mA and ambient temperature of 20 ° C to 80 ° C, the side-mode suppression ratio of the laser light generated by the distributed feedback semiconductor laser device 100 is greater than 40dB, so it has good single model characteristics, and its wavelength shift per current The amount and the amount of wavelength shift per temperature are 34 pm/mA and 47 pm/K, respectively.

FIG. 9 is a measurement result of a small signal electrical / optical response (E / O response) S ₂₁ corresponding to a distributed feedback laser light generated by a distributed feedback semiconductor laser device according to an embodiment of the present invention under different operating currents of 60 mA . It can be known from FIG. 9 that the -3dB bandwidth at the operating current of 20mA to 80mA is greater than 10GHz.

Further, a pulse pattern generator (PPG) is used to generate (2 ³¹ -1) a non-return-to-zero pseudo-random binary sequence (PRBS), and its peak-to-peak The bias voltage is 2V, and at the receiving end, a PIN photodetector set at a rate of 32Gb / s is used to receive the optical signal, and the measurement result is displayed by the sampling oscilloscope, and 10Gb / s is non-return-to-zero; The extinction ratio of the (NRZ) signal is set to 5.7dB. FIG. 10 shows the relationship between the bit error rate (BER) and the received power and the optical eye diagram measurement results of the distributed feedback laser light generated by the distributed feedback semiconductor laser device 100 at an operating current of 60 mA. FIG. 10 shows that there is no error in operation when the transmission rate of the back-to-back (BTB) transmission method is 10 Gb / s.

FIG. 11 is a schematic perspective view of a distributed feedback semiconductor laser device 200 according to another embodiment of the present invention. As shown in FIG. 11, the distributed feedback semiconductor laser device 200 includes an active layer 210, a first grating layer 220, and a second The grating layer 230, the buffer layer 240, the substrate 250, the cladding layer 260, the contact layer 270, the passivation layer 280, the upper electrode layer 292, and the lower electrode layer 294, wherein the active layer 210 includes a multiple quantum well layer structure 211 and is located in multiple quantum wells, respectively. The lower separation confined heterostructure 212 and the upper separation confined heterostructure 213 on opposite sides of the well layer structure 211. The first grating layer 220 includes a first grating structure 221 and a coating 222, and the second grating layer 230 includes a second grating structure. 222 and coating 232. Please refer to FIG. 12 together, which is a partial cross-sectional view of a distributed feedback semiconductor laser device 200. As shown in FIGS. 11 and 12, the first grating layer 220 and the second grating layer 230 are sequentially stacked below the active layer 210, wherein the grating periods of the first grating structure 221 and the second grating structure 231 are different. In the embodiment shown in FIG. 12, the grating period P1 of the first grating structure 221 is greater than the grating period P2 of the second grating structure 231. In other embodiments, the grating period P1 of the first grating structure 221 may be smaller than the grating period P2 of the second grating structure 231. The equivalent grating period of the combination of the first grating structure 221 and the second grating structure 231 is (2 × P1 × P2) / (P1 + P2). The coating layer 222 covers the first grating structure 221 and fills the space in the first grating structure 221, and the coating layer 232 covers the second grating structure 231 and fills the space in the second grating structure 231. The refractive index of the first grating structure 221 and the second grating structure 221 may be greater than the refractive indexes of the coating layers 222 and 232, respectively.

The material of the first grating structure 221 and the second grating structure 231 may be N-type indium gallium arsenide, and the material of the coating layers 222 and 232 may be N-type indium phosphide. In other embodiments, the first grating structure 221, the second grating structure 231, and the coatings 222, 232 may be made of other materials. For example In other words, the first grating structure 221 and the second grating structure 231 may be composed of N-type aluminum indium gallium phosphide, and the coating layers 222 and 232 may be composed of N-type gallium arsenide.

The buffer layer 240 is located above the second grating layer 230 and may be composed of N-type indium phosphide. The substrate 250 is located under the buffer layer 240, and the thickness of the substrate 250 may be about 100 μm, and the substrate 250 may be made of indium phosphide. The cladding layer 260 is located above the buffer layer 240 and has a thickness of about 2 μm. The cladding layer 260 can be made of P-type indium phosphide.

In some embodiments, an N-type In _0.53 Al _x Ga _(0.47-x) As layer with a thickness of about 10 nm may be further included between the active layer 210 and the first grating layer 220, and the active layer 210 and the cladding layer 260 may further include a P-type In _0.53 Al _x Ga _(0.47-x) As layer with a thickness of about 50 nm, where x is 0.36 to 0.44.

The configuration of the contact layer 270, the passivation layer 280, the upper electrode layer 292, and the upper electrode layer 294 may be respectively the same as the configuration of the contact layer 170, the passivation layer 180, the upper electrode layer 192, and the upper electrode layer 194 in the distributed feedback semiconductor laser device 100 Similar, so please refer to the previous paragraphs for related explanations, which will not be repeated here.

Similarly, according to application requirements, a high reflection film and an anti-reflection film may be plated on both ends of the laser resonance cavity constituting the distributed feedback semiconductor laser device 200, respectively, and an anti-reflection film and a high-reflection film may be plated on both sides. Have a high-reflection film, all coated with anti-reflection film, or no coating. In addition, in the distributed feedback semiconductor laser device 200, the relative positions of the first grating structure 221 and the second grating structure 231 to the laser cavity may be aligned or misaligned.

An example of a manufacturing method of the distributed feedback semiconductor laser device 200 is as follows. First, a substrate 250 is provided, and then on a plane of the substrate 250 The buffer layer 240, the second grating layer 230, and the first grating layer 220 are sequentially formed. Examples of the method for forming the first grating layer 220 and the second grating layer 230 are as follows. First, a grating material layer is deposited on the buffer layer 240, and then a grating structure region is defined on the grating material layer, and a laser interference lithography process and wet etching are performed to form a second grating structure 231. A coating 232 is formed on the grating structure 231. In other embodiments, a partial coating 232 and a grating material layer may be formed on the buffer layer 240 first, and then a laser interference lithography process and wet etching are performed on the grating material layer to form a second grating. Structure 231, and then another coating 232 is formed on the second grating structure 231. After the second grating layer 230 is completed, another grating material layer is deposited on the second grating layer 230, and then a laser interference lithography process and wet etching are performed on the grating material layer to form a first grating structure 221. A coating layer 222 is formed on the first grating structure 221.

After that, an active layer 210 is formed on the first grating layer 220 and includes a lower separated confined heterostructure 212, a multiple quantum well layer structure 211, and an upper separated confined heterostructure 213, which are sequentially stacked from bottom to top. Then, a cladding layer 260 and a contact layer 270 are formed on the active layer 210 and a ridge region is defined. Then, a passivation layer 280 and an upper electrode layer 292 are sequentially formed on the cladding layer 260 and the contact layer 270 to distribute the A ridge waveguide structure is formed on the feedback semiconductor laser device 200, and a lower electrode layer 294 is finally formed on the other plane of the substrate 250.

FIG. 13 is a schematic perspective view of a distributed feedback semiconductor laser device 300 according to another embodiment of the present invention. As shown in FIG. 13, the distributed feedback semiconductor laser device 300 includes an active layer 310, a first grating layer 320, and a second The grating layer 330, the buffer layer 340, the substrate 350, the cladding layer 360, the contact layer 370, the passivation layer 380, the upper electrode layer 392, and the lower electrode layer 394. The active layer 310 includes a multiple quantum well layer structure 311 and multiple quantum well layers. The lower separation confined heterostructure 312 and the upper separation confined heterostructure 313 on opposite sides of the well layer structure 311. The first grating layer 320 includes a first grating structure 321 and a coating layer 322, and the second grating layer 330 includes a second grating structure. 322 and coating 332. Please refer to FIG. 14 together, which is a partial cross-sectional view of a distributed feedback semiconductor laser device 300. As shown in FIGS. 13 and 14, the first grating layer 320 and the second grating layer 330 are located above and below the active layer 310, respectively, and the grating periods of the first grating structure 321 and the second grating structure 331 are different. In the embodiment shown in FIG. 14, the grating period P1 of the first grating structure 321 is greater than the grating period P2 of the second grating structure 331. In other embodiments, the grating period P1 of the first grating structure 321 may be smaller than the grating period P2 of the second grating structure 331. The equivalent grating period of the combination of the first grating structure 321 and the second grating structure 331 is (2 × P1 × P2) / (P1 + P2). The coating layer 322 covers the first grating structure 321 and fills the space in the first grating structure 321, and the coating layer 332 covers the second grating structure 331 and fills the space in the second grating structure 331. The refractive index of the first grating structure 321 and the second grating structure 321 may be larger than the refractive indexes of the coating layers 322 and 332, respectively.

The material of the first grating structure 321 may be P-type indium gallium arsenide, and the material of the coating layer 322 may be P-type indium phosphide. In addition, the material of the second grating structure 331 may be N-type indium gallium arsenide, and the material of the coating layer 332 may be N-type indium phosphide. In other embodiments, the first grating structure 321, the second grating structure 331, and the coatings 322, 332 may be made of other materials. to make. For example, the first grating structure 321 and the second grating structure 331 may be respectively composed of P-type aluminum indium gallium phosphide and N-type aluminum indium gallium phosphide, and the coatings 322 and 332 may be respectively made of p-type gallium arsenide and N-type gallium arsenide.

The buffer layer 340 is located below the second grating layer 330 and may be composed of N-type indium phosphide. The substrate 350 is located under the buffer layer 340, and the thickness of the substrate 350 may be about 100 μm, and the substrate 350 may be made of indium phosphide. The cladding layer 360 is located above the first grating structure 320 layer, and the thickness thereof may be about 2 μm, and it may also be made of indium phosphide.

In some embodiments, a P-type In _0.53 Al _x Ga _(0.47-x) As layer having a thickness of about 50 nm may be further included between the active layer 310 and the first grating layer 320, and the active layer 310 and the buffer layer 320 may be included. may further comprise a thickness of about 10nm between the N-type _{in 0.53 Al x Ga (0.47-} x) as layer, where x is from 0.36 to 0.44.

The configuration of the contact layer 370, the passivation layer 380, the upper electrode layer 392, and the upper electrode layer 394 may be respectively the same as that of the contact layer 170, the passivation layer 380, the upper electrode layer 392, and the upper electrode layer 194 in the distributed feedback semiconductor laser device 100 Similar, so please refer to the previous paragraphs for related explanations, which will not be repeated here.

Similarly, according to application requirements, both ends of the laser resonant cavity constituting the distributed feedback semiconductor laser device 300 can be plated with a high-reflection film and an anti-reflection film, respectively, an anti-reflection film and a high-reflection film, and both can be plated. Have a high-reflection film, all coated with anti-reflection film, or no coating. In addition, in the distributed feedback semiconductor laser device 300, the relative positions of the first grating structure 321 and the second grating structure 331 to the laser cavity may be aligned or misaligned.

An example of a manufacturing method of the distributed feedback semiconductor laser device 300 is as follows. First, a substrate 350 is provided, and then a buffer layer 340 and a second grating layer 330 are sequentially formed on a plane of the substrate 350. The formation method of the second grating layer 330 may be similar to the formation method of the second grating layer 230 of the distributed feedback semiconductor laser device 200. After that, an active layer 310 is formed on the second grating layer 330, which includes a lower separated confined heterostructure 312, a multiple quantum well layer structure 311, and an upper separated confined heterostructure 313, which are sequentially stacked from bottom to top. Then, a first grating layer 320 is formed on the active layer 210, and then a cladding layer 360 and a contact layer 370 are formed on the first grating layer 320, and a ridge region is defined. The formation method of the first grating layer 320 may be similar to the formation method of the first grating layer 120 of the distributed feedback semiconductor laser device 100. Thereafter, a passivation layer 380 and an upper electrode layer 392 are sequentially formed on the cladding layer 360 and the contact layer 370 to form a ridge waveguide structure on the distributed feedback semiconductor laser device 300, and finally on another plane of the substrate 350 A lower electrode layer 394 is formed thereon.

The only difference between the distributed feedback semiconductor laser devices 100, 200, and 300 is that the first grating layer 120 and the second grating layer 130 in the distributed feedback semiconductor laser device 100 are above the active layer 110. The distributed feedback semiconductor The first grating layer 220 and the second grating layer 230 in the laser device 200 are under the active layer 210, and the first grating layer 320 and the second grating layer 330 in the distributed feedback semiconductor laser device 300 are respectively Above and below the active layer 310. However, since the two-layer grating layer is disposed on the upper side, the lower side, or the opposite sides of the active region, the equivalent refractive indices obtained are the same, so the phase shift characteristics of the distributed feedback semiconductor laser device 100, 200, and 300 The same. Particularly, in the distributed feedback semiconductor laser device 200, Since the first grating layer 220 and the second grating layer 230 are below the active layer 210, the thickness of the structure above the active layer 210 becomes thinner, so that the leakage current and the critical current value are further reduced, and the light emitting efficiency of the laser element is improved.

FIG. 15 is a partial cross-sectional view of a distributed feedback semiconductor laser device 400 according to another embodiment of the present invention. In FIG. 15, the grating layer 420 is located on the active layer 410 and includes an amplitude Molewave grating structure. This grating structure can be generated by two laser holographic interference lithography steps, in which the first exposure and the second exposure Interference fringes are generated at different periods. Please refer to FIGS. 16A to 16D together, where FIG. 16A is a schematic waveform diagram of the amplitude Molewave grating structure, and FIGS. 16B to 16D are different examples of the grating layer 420 respectively. Waveform of the composite wave W1 + W2 of the waveform shown in Figure 16A is similar to FIG. 3, which also comprises a short period and long period P _S P _L. Each of the grating structures 421, 421 ', and 421 "shown in Figs. 16B to 16D is a part of the grating layer 420 and is an amplitude Morale wave grating structure. The difference between the grating structures 421, 421', and 421" is that the grating structure 421 has periodic height and depth changes. The grating structure 421 'has only periodic depth changes, while the grating structure 421 "has only periodic height changes. The above-mentioned periodic height changes and depth changes correspond to two different sine functions. The superimposed waveforms are, for example, the superimposed waveforms of the sine waves W1 and W2 shown in FIG. 3, that is, the waveforms of the synthesized waves W1 + W2. In addition, the height of the microstructure in each grating structure 421, 421 ', 421 ", The depth of the groove and the height and depth variation period (ie, the long period _PL ) of the groove can be adjusted by the exposure time or dose of the holographic interference lithography process.

Each grating structure 421, 421 ', 421 "may be covered by a coating with a lower refractive index. According to the distributed feedback semiconductor laser device 400, Kind, the material of the grating structure 421, 421 ', 421 "may be P-type or N-type indium gallium arsenide, and the material of the coating layer may be P-type or N-type indium phosphide. In addition, in other embodiments, The grating layer 420 may be located under the active layer 410.

As for the other components of the distributed feedback semiconductor laser device 400 not shown in FIG. 15, such as a buffer layer, a substrate, a cladding layer, a contact layer, a passivation layer, an upper electrode layer, and a lower electrode layer, etc., they can be respectively separated from the foregoing. The buffer layer 140, the substrate 150, the cladding layer 160, the contact layer 170, the passivation layer 180, the upper electrode layer 192, and the lower electrode layer 194 of the distributed feedback semiconductor laser device 100 are similar to the distributed feedback semiconductor laser device, respectively. The buffer layer 240, the substrate 250, the cladding layer 260, the contact layer 270, the passivation layer 280, the upper electrode layer 292, and the lower electrode layer 294 of 200 are similar, so for related descriptions, please refer to the previous paragraphs, and are not repeated here.

Although the present invention has been disclosed as above with the examples, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make some modifications and retouching without departing from the spirit and scope of the present invention. The protection scope of the present invention shall be determined by the scope of the attached patent application.

Claims (9)

A distributed feedback (DFB) semiconductor laser device includes: an active layer; a first grating layer including a first grating structure having a first grating period; and a second grating layer including having a The second grating structure of the second grating period, the first grating period is substantially different from the second grating period; wherein the active layer, the first grating layer, and the second grating layer are stacked on top of each other, and the distribution The equivalent grating period of the feedback semiconductor laser device is (2 × P1 × P2) / (P1 + P2), where P1 and P2 are the first grating period and the second grating period, respectively. The distributed feedback semiconductor laser device according to item 1 of the scope of patent application, wherein the first grating layer and the second grating layer are located on the same side of the active layer. The distributed feedback semiconductor laser device according to item 2 of the patent application scope, wherein the second grating layer is directly stacked on the first grating layer. The distributed feedback semiconductor laser device according to item 1 of the scope of the patent application, wherein the first grating layer and the second grating layer are located on opposite sides of the active layer, respectively. The distributed feedback semiconductor laser device according to item 1 of the scope of the patent application, wherein the difference between the first grating period and the second grating period is substantially lower than 1 nm. The distributed feedback semiconductor laser device according to item 1 of the scope of the patent application, wherein a filling factor of the first grating structure and the second grating structure is about 0.4 to 0.5. The distributed feedback semiconductor laser device according to item 1 of the scope of the patent application, wherein the optical confinement factor of the first grating structure and the second grating structure are substantially the same. A distributed feedback (DFB) semiconductor laser device includes: an active layer; and a grating layer including a grating structure; wherein the active layer and the grating layer are stacked on top of each other, and the grating structure has Periodic height or depth changes. The height and depth changes of the grating structure correspond to the waveforms of two different sine functions. The distributed feedback semiconductor laser device according to item 8 of the scope of the patent application, wherein the height of the microstructure in the grating structure, the depth of the groove and the height and depth of its composition are changed by the holographic interference lithography process. Exposure time or dose adjustment.