KR102642580B1 - Tunable distributed feedback laser diode with thin film heater - Google Patents

Abstract

The present invention relates to a tunable distributed feedback (DFB) laser diode with an integrated thin film heater.
A thin film heater integrated tunable distribution feedback laser diode according to an embodiment of the present invention includes a substrate, a lower clad layer, a diffraction grating, an active layer, an upper clad layer, an ohmic layer, an upper electrode, and an insulating layer laminated on the substrate. , a thin film heater including a heating area located on the insulating layer, wherein the length of the diffraction grating is formed to be smaller than the length of the active layer waveguide, and the length of the heating area of the thin film heater is a diffraction grating on which the diffraction grating is disposed. It is characterized by being longer than or equal to the length of the region.

Description

Thin film heater integrated wavelength variable distribution feedback laser diode {TUNABLE DISTRIBUTED FEEDBACK LASER DIODE WITH THIN FILM HEATER}

The present invention relates to a tunable distributed feedback (DFB) laser diode with an integrated thin film heater.

Recently, with the advent of high-speed Internet and various multimedia services, there is an increasing demand for the development of optical communication technology to provide large amounts of information. Representative optical communication technologies, Wavelength Division Multiplexing Passive Optical Network technology and Coherent Optical Network technology, require a key element, a tunable laser diode.

Tunable laser diodes with an integrated thin film heater change the wavelength by changing the internal temperature of the semiconductor laser diode using a thin film heater. This thin-film heater-integrated tunable laser diode has the advantage of being able to continuously change the wavelength and having a narrow oscillation line width. However, the range of wavelength tuning for thin-film heater-integrated tunable laser diodes is somewhat limited, and as the range of wavelength tuning increases, the side mode suppression ratio (Side Mode Suppression Ratio, SMSR) decreases. may decrease or mode hopping may occur.

The technical problem to be achieved by the present invention is to provide a thin-film heater-integrated tunable DFB laser diode that is capable of continuous wavelength tuning without mode hopping and can obtain excellent side mode suppression ratio (SMSR).

A thin film heater integrated tunable distribution feedback laser diode according to an embodiment of the present invention includes a substrate, a lower clad layer, a diffraction grating, an active layer, an upper clad layer, an ohmic layer, an upper electrode, and an insulating layer laminated on the substrate. , a thin film heater including a heating area located on the insulating layer, wherein the length of the diffraction grating is formed to be smaller than the length of the active layer waveguide, and the length of the heating area of the thin film heater is a diffraction grating on which the diffraction grating is disposed. It is characterized by being longer than or equal to the length of the region.

Depending on the embodiment, the heating area of the thin film heater and the diffraction grating area may overlap each other, and the heating area of the thin film heater may be arranged to completely cover the diffraction grating area.

Depending on the embodiment, the line width of the heating area of the thin film heater may be uniform.

Depending on the embodiment, the line width of the heating area of the thin film heater may be tapered.

Depending on the embodiment, the line width of the heating area of the thin film heater may be wide at the center of the diffraction grating and may be tapered to decrease as the distance from the center of the diffraction grating increases.

Depending on the embodiment, the diffraction grating may be located within the lower clad layer, the active layer, or the upper clad layer.

Depending on the embodiment, the diffraction grating may be one of a λ/4 phase shift diffraction grating, a loss-coupled diffraction grating, a gain-coupled diffraction grating, and an index-coupled diffraction grating.

Depending on the embodiment, the thin film heater is a single heater containing at least one of chromium (Cr), gold (Au), titanium (Ti), platinum (Pt), nickel (Ni), aluminum (Al), and silver (Ag). It may be formed as a thin film or one or more composite layers.

Depending on the embodiment, it may further include an anti-reflective film formed on cleavage surfaces at both ends of the laser diode.

Depending on the embodiment, the laser diode may further include an anti-reflective film formed on one cleavage surface among the cleavage surfaces and a highly reflective film formed on the other cleavage surface.

Depending on the embodiment, the insulating layer may be composed of a silicon oxide layer (SiO2) or a silicon nitride layer (SiNx) interposed between the upper electrode and the thin film heater to electrically insulate the upper electrode and the thin film heater. there is.

Depending on the embodiment, the active layer may be composed of a bulk layer of InGaAsP, InGaAlAs, InGaNAs, or a multiple quantum well.

Depending on the embodiment, at least one of a semiconductor optical amplifier, a field absorption optical modulator, and a Mach-Zehnder optical modulator may be integrated into the laser diode.

Depending on the embodiment, the ohmic layer and upper electrode of the laser diode and the semiconductor optical amplifier or the optical modulator may be separated.

Depending on the embodiment, an insulating trench or ion implantation region may be additionally formed between the laser diode and the separated ohmic layer and upper electrode of the semiconductor optical amplifier or the optical modulator.

Depending on the embodiment, the laser diode may have a ridge-shaped waveguide, and the heating area of the thin film heater may be located on one side of the bottom of the ridge-shaped waveguide.

The present invention is a thin film heater in which the length of the heating area is greater than or equal to the length of the diffraction grating area. We propose a tunable DFB laser diode with integrated thin film heater. According to the present invention, when heating a tunable DFB laser diode using a thin film heater, it can be heated to have a uniform temperature distribution in the resonance direction of the tunable DFB laser diode. Accordingly, continuous wavelength tuning is possible without mode hopping, and a thin-film heater integrated tunable DFB laser diode with excellent side mode suppression ratio (SMSR) can be obtained.

1 is a plan view showing an example of a thin film heater.
Figure 2(a) is a plan view showing an example of a thin film heater integrated tunable DFB laser diode.
FIG. 2(b) is a cross-sectional view in the resonance direction of the thin film heater integrated tunable DFB laser diode shown in FIG. 2(a).
FIG. 2(c) is a vertical cross-sectional view of the thin film heater integrated tunable DFB laser diode shown in FIG. 2(a).
Figure 3(a) is a plan view of a thin film heater integrated tunable DFB laser diode according to an embodiment of the present invention.
FIG. 3(b) is a cross-sectional view in the resonance direction of the thin film heater integrated tunable DFB laser diode shown in FIG. 3(a).
FIG. 4(a) is a graph showing optical spectra measured while increasing the power applied to the thin film heater in the tunable DFB laser diode integrated with the thin film heater shown in FIGS. 2(a) to 2(c).
Figure 4(b) is a measurement taken while increasing the power applied to the thin film heater in the tunable DFB laser diode integrated with a thin film heater according to the embodiment shown in Figures 3(a) to 3(b), which is an embodiment of the present invention. This is a graph showing light spectra.
Figure 4(c) shows the thin film heater integrated tunable DFB laser diode shown in Figures 2(a) to 2(c) and the embodiment of the present invention shown in Figures 3(a) to 3(b). This is a graph showing the side mode suppression ratio (SMSR) according to the power applied to the thin film heater in the thin film heater integrated tunable DFB laser diode.
Figure 5 is a plan view of a thin film heater integrated tunable DFB laser diode according to another embodiment of the present invention.
Figure 6 is a cross-sectional view in the resonance direction of a thin film heater integrated tunable DFB laser diode according to another embodiment of the present invention.
Figure 7 is a cross-sectional view in the resonance direction of a thin film heater integrated tunable DFB laser diode according to another embodiment of the present invention.
Figure 8(a) is a plan view of a thin film heater integrated tunable DFB laser diode according to another embodiment of the present invention.
FIG. 8(b) is a vertical cross-sectional view of the thin film heater integrated tunable DFB laser diode shown in FIG. 8(a).

Hereinafter, with reference to the attached drawings, embodiments of the present invention and other matters necessary for those skilled in the art to easily understand the contents of the present invention will be described in detail. However, the examples described below are merely illustrative regardless of whether they are expressed or not. In other words, the present invention is not limited to the embodiments disclosed below, but may be modified and implemented in various forms.

1 is a plan view showing an example of a thin film heater.

Referring to FIG. 1, the thin film heater 10 includes a thin film heater pad 3 that is bonded to a wire, for example, to receive power, and a thin film heater bridge for transmitting power applied to both ends of the thin film heater pad 3. 2), and a thin film heater heating area 1 in which most of the power applied to the thin film heater 10 is converted into heat. Among the pad 3, bridge 2, and heating area 1 of the thin film heater 10, the line width W3 of the pad 3 is the widest, and the line width W1 of the heating area 1 is the narrowest. For example, the pad 3 has a line width W3 of about 100 μm or more, the bridge 2 has a line width W2 of about 20 μm to 30 μm, and the heating area 1 has a line width W1 of about 3 μm to 10 μm. You can have Accordingly, most of the power applied to both ends of the pad 3 is applied to the heating area 1, which has the smallest line width W1 and the highest resistance value, and is converted into heat.

Meanwhile, in order to compare the resistance values of the heating area (1), bridge (2), and pad (3) of the thin film heater (10), their line widths (W1, W2, W3) were compared, but in addition, their constituent materials , the resistance value may be adjusted by adjusting at least one of the cross-sectional area, length, and thickness. That is, in constructing the thin film heater 10, the pad 3 to which power is applied and the bridge 2 that transmits the power applied to the pad 3 to the heating area 1 are designed to reduce heat loss. The resistance values of the pad 3 and the bridge 2 can be designed to be relatively small. In addition, the resistance value of the heating area (1) can be designed to be larger than the resistance value of the pad (3) and bridge (2) so that most of the power supplied to the thin film heater (10) is converted into heat. .

Depending on the embodiment, the thin film heater 10 is made of platinum (Pt), gold (Au), chromium (Cr), nickel (Ni), titanium (Ti), aluminum (Al), and It may be formed as a single thin film or one or more composite layers containing at least one of silver (Ag). Additionally, depending on the embodiment, the thin film heater 10 may be composed of a multi-layer metal film. The heating area 1 of the thin film heater 10 may be made of the same material and/or thickness as at least one of the bridge 2 and the pad 3. Alternatively, the heating area 1 of the thin film heater 10 may be made of a different material and/or thickness than at least one of the bridge 2 and the pad 3. For example, the heating area (1), bridge (2), and pad (3) of the thin film heater 10 are all formed of the same metal material, but the thickness of the metal constituting the bridge (2) and pad (3) is different from the heating area. By depositing the pad thicker than the thickness of (1), most of the power applied to the pad (3) can be generated in the heating area (1). In addition, depending on the embodiment, the heating area 1 of the thin film heater 10 is composed of a single metal film, and the bridge 2 and pad 3 are composed of a multi-layer metal film, so that the bridge 2 and pad 10 are composed of a single metal film. The resistance in (3) can be further lowered.

Figure 2(a) is a plan view showing an example of a thin film heater integrated tunable DFB laser diode. And, Figure 2(b) is a cross-sectional view in the resonance direction of the thin film heater integrated tunable DFB laser diode shown in Figure 2(a), and Figure 2(c) is a thin film heater integrated tunable DFB shown in Figure 2(a). This is a vertical cross-sectional view of a laser diode. Specifically, FIG. 2(b) is a cross-sectional view taken along the X-X' direction of FIG. 2(a), and FIG. 2(c) is a cross-sectional view taken along the Y-Y' direction of FIG. 2(a).

Hereinafter, the structure and manufacturing method of the thin film heater integrated tunable DFB laser diode 100 will be described with reference to FIGS. 2(a) to 2(c). For convenience, when describing FIGS. 2(a) to 2(c), the same or similar components as those in FIG. 1 will be assigned the same reference numerals, and detailed description thereof will be omitted.

First, the first n-InP lower clad layer 22a is grown on the n-InP substrate 21, and the λ/4-phase shift diffraction grating 4 is formed by electron beam lithography or holography.

In order to flatten the formed diffraction grating 4, a second n-InP lower clad layer 22b and an active layer 5 are grown on the diffraction grating 4. The first n-InP lower clad layer 22a and the second n-InP lower clad layer 22b constitute the lower clad layer (n-InP clad layer) of the thin film heater integrated tunable DFB laser diode 100. And, the active layer 5 constitutes an active layer waveguide of the thin film heater integrated tunable DFB laser diode 100.

Meanwhile, in Figure 2(b), an embodiment in which the diffraction grating 4 is formed in the lower clad layer (n-InP clad layer) 22 of the thin film heater integrated tunable DFB laser diode 100 is disclosed, but the present invention This is not limited to this. For example, the diffraction grating 4 may be formed in the upper clad layer (p-InP clad layer) 23 or the active layer 5 of the thin film heater integrated tunable DFB laser diode 100.

Depending on the embodiment, the active layer 5 may be an InGaAsP bulk layer with a wavelength of 1.55 μm or a multi quantum well (MQW) composed of an InGaAsP well and an InGaAsP barrier. In addition, an InGaAsP separated confinement heterostructure (SCH) having a larger band gap than the active layer 5, for example, 1.1 to 1.3 μm, can be added to the upper and lower parts of the active layer 5.

Depending on the embodiment, the active layer 5 may be manufactured in the form of a waveguide with a line width of 1 to 1.5 μm through photo lithography and etching processes. Additionally, a current blocking layer 27 may be grown on the left and right sides of the active layer 5 waveguide to form a planar buried heterostructure (PBH). The current blocking layer 27 may use a p-InP/n-InP/p-InP layer or a Fe-doped InP layer with semi-insulating properties.

On top of the active layer 5, a p-InP clad layer (upper clad layer of the thin film heater integrated tunable DFB laser diode 100) 23 and a p ⁺ -InGaAs ohmic layer 24 are formed. In addition, an upper ohmic layer 25 is formed on the p ⁺ -InGaAs ohmic layer 24 so that current can be injected into the DFB laser diode 100, A lower ohmic metal layer 20 is formed on the opposite side (eg, lower side) of the n-InP substrate 21. The upper ohmic layer 25 becomes the upper electrode of the DFB laser diode 100, and the lower ohmic metal layer 20 becomes the lower electrode of the DFB laser diode 100.

An insulating layer 26 such as silicon nitride (SiN _x ) or silicon oxide (SiO ₂ ) is deposited on the upper electrode 25 to electrically insulate it from the thin film heater 10 . That is, the insulating layer 26 is interposed between the upper electrode 25 of the thin film heater integrated tunable DFB laser diode 100 and the thin film heater layer (e.g., the thin film heater heating area 1), and the thin film heater 10 ) and the DFB laser diode upper electrode 25 are electrically insulated.

The fabricated thin film heater integrated tunable DFB laser diode 100 is cleaved. Depending on the embodiment, anti-reflective thin films 7 and 8 may be formed (eg, deposited) on both side walls of the cleaved DFB laser diode 100.

In this thin-film heater integrated tunable laser diode 100, the oscillation wavelength is expressed as Equation 1 below.

In Equation 1, λ means the oscillation wavelength, n _eff means the effective refractive index, and Λ means the period of the diffraction grating.

The period (Λ) of the diffraction grating is fixed to a predetermined value during manufacturing. For example, the period (Λ) of the diffraction grating may be fixed to 237 nm. The effective refractive index (n _eff ) is determined by the refractive index of the active layer (5).

Power is applied to the thin film heater 10 to change the oscillation wavelength of the thin film heater integrated tunable DFB laser diode 100. Then, the power applied to the thin film heater 10 is transmitted to the thin film heater heating area 1, and heat is generated in the thin film heater heating area 1 due to Joule's heat, thereby causing the DFB laser diode 100. Raise the temperature. When the temperature of the DFB laser diode 100 increases, the effective refractive index (n _eff ) of the active layer 5 changes and the oscillation wavelength changes. As the temperature rises, the band gap of the active layer 5 shifts to red, so the effective refractive index (n _eff ) of the active layer 5 increases. Therefore, as the power applied to the thin film heater 10 increases, the temperature of the thin film heater heating area 1 increases, and as a result, the oscillation wavelength of the diffraction grating 4 also transitions to a long wavelength.

Generally, when cleaving the DFB laser diode 100, the precision of the cleavage equipment is approximately 10㎛. Therefore, in order to leave an allowable margin (M) between the cleavage surfaces (both end surfaces) of the DFB laser diode 100, the thin film heater 10 is lengthened to be located approximately 10㎛ inside from the cleavage surface of the DFB laser diode 100. form small. Additionally, when viewed from the resonance direction (X-X') of the DFB laser diode 100, there is a length occupied by the thin film heater bridge 2. Therefore, in the thin film heater integrated tunable DFB laser diode 100 disclosed in FIGS. 2(a) to 2(c), the thin film heater heating area 1 is located in the diffraction grating area 40 where the diffraction grating 4 is disposed. Compared to the length (eg, horizontal length), each is approximately 30㎛ to 40㎛ shorter from the central point (0).

In the thin film heater integrated tunable DFB laser diode 100 where the length of the thin film heater heating area 1 is shorter than the length of the diffraction grating area 40, when power is applied to the thin film heater 10 for wavelength tuning, the thin film heater The internal temperature of the DFB laser diode 100 is highest at the central point (0) of the heater heating area (1), and the temperature of the edge area (near the cleavage plane) is relatively lower than the central point (0).

Regarding this temperature non-uniformity phenomenon, a paper published by T. Kameda et al. ("A DBR laser employing passive-section heaters, with 10.8 nm tuning range and 1.6 MHz linewidth", IEEE Photonics Technology Letters, pp. 608, Vol.5, No. 6, 1993), the internal temperature of the laser diode shows that the central point of the thin film heater heating area is relatively higher than the edge area, and the higher the power applied to the thin film heater, the higher the temperature is at the center in the resonance direction of the laser diode. The temperature difference between the point and the edge area shows a tendency to increase.

As previously explained in Equation 1, the oscillation wavelength of the tunable DFB laser diode 100 using the thin film heater 10 uses the change in effective refractive index (n _eff ) according to the temperature change of the thin film heater 10. However, when the temperature becomes non-uniform in the resonance direction (XX' direction) of the DFB laser diode 100, the effective refractive index (n _eff ) of the DFB laser diode 100 also becomes non-uniform in the resonance direction (XX' direction), causing the DFB laser The single mode oscillation characteristics of the diode 100 deteriorate. In addition, as mentioned in the paper by T. Kameda et al., as the applied power of the thin film heater 10 increases to increase the range of wavelength tuning, the temperature difference at the edge area compared to the center point of the DFB laser diode 100 increases. The single mode oscillation characteristics become worse.

The single-mode oscillation characteristic of the DFB laser diode 100 is a very important characteristic in WDM optical communication based on wavelength division, and as an indicator of the single-mode oscillation characteristic, the side mode suppression ratio is at least 35 dB or more. It must be.

Accordingly, the present invention is a thin-film heater integrated wavelength tunable DFB that heats the diffraction grating 4 so that the temperature distribution is uniform, enabling continuous wavelength tuning without mode hopping even when changing the wavelength, and obtaining excellent side mode suppression ratio (SMSR). Various embodiments of laser diodes are proposed.

Figure 3(a) is a plan view of a thin film heater integrated tunable DFB laser diode according to an embodiment of the present invention. And, FIG. 3(b) is a cross-sectional view in the resonance direction of the thin film heater integrated tunable DFB laser diode shown in FIG. 3(a), and is a cross-sectional view along the X-X' direction of FIG. 2(a). Meanwhile, since the cross-section along the vertical direction (Y-Y' direction) of FIG. 3(a) will be substantially the same or similar to FIG. 2(c), the vertical cross-section of FIG. 3(a) will be omitted. In addition, when describing FIGS. 3(a) to 3(b), the same or similar components as those in FIGS. 1 to 2(c) are assigned the same reference numerals, and detailed description thereof will be omitted.

Referring to FIGS. 3(a) to 3(b) , in the thin film heater integrated tunable DFB laser diode 200 according to this embodiment, the length of the diffraction grating 4 is an active layer waveguide implemented with the active layer 5. and the length of the thin film heater heating area 1 is formed to be longer than the length of the diffraction grating area 50. In particular, in this embodiment, the thin film heater heating area 1 is formed to completely include (that is, cover) the diffraction grating area 50. More specifically, in this embodiment, the length of the thin film heater heating area 1 is smaller than the length of the waveguide of the active layer 5 and is formed to be greater than or equal to the length of the diffraction grating area 50 (or diffraction grating 4). .

Depending on the embodiment, the thin film heater heating area 1 may be formed to have a uniform line width. Here, the diffraction grating area 50 where the diffraction grating 4 is formed is an area for oscillating a single mode, and the active waveguide area 60 with only the active layer 5 without the diffraction grating 4 is the diffraction grating area 50. This is the area where the single mode generated in is output without amplification or loss.

In this way, when the thin film heater heating area 1 is formed to completely include the diffraction grating area 50, the temperature distribution of the diffraction grating 4 in the resonance direction (XX' direction) of the DFB laser diode 200 even during heating. becomes uniform. thus, It is possible to improve the temperature non-uniformity phenomenon within the diffraction grating 4 in the thin film heater integrated tunable DFB laser diode 100 of the comparative example shown in FIGS. 2(a) to 2(c). That is, according to an embodiment of the present invention, by heating the diffraction grating 4 so that the temperature distribution is uniform, continuous wavelength change is possible without mode hopping even when the wavelength is changed, and excellent side mode suppression ratio (SMSR) is achieved. ) can be obtained.

According to the embodiment, in order to more effectively improve the temperature non-uniformity problem within the diffraction grating 4 in the thin film heater integrated tunable DFB laser diode 100 of the comparative example shown in FIGS. 2(a) to 2(c), The diffraction grating 4 may be formed in the p-InP clad layer (upper clad layer) 23, which is the upper part of the active layer 5. Alternatively, the diffraction grating 4 may be formed directly on the active layer 5 to form a gain-coupled grating.

Depending on the embodiment, the diffraction grating 4 may be one of a λ/4 phase shift diffraction grating, an index-combined diffraction grating, and a gain-combined diffraction grating. Alternatively, the diffraction grating 4 may be a loss-coupled grating formed of InGaAs.

Depending on the embodiment, the active layer 5 may be a bulk layer such as InGaAsP, InGaAlAs, InGaNAs, or a multi-quantum well.

Depending on the embodiment, the waveguide structure of the active layer 5 may be in the form of a flat buried structure, a ridge, a stripe, and/or a rib waveguide.

Depending on the embodiment, at least one of the anti-reflective films 7 and 8 formed on the cleavage surfaces at both ends of the thin film heater integrated tunable DFB laser diode 200 may be formed as a highly reflective film. For example, an anti-reflective film may be deposited on one cleavage surface of the DFB laser diode 100, and a highly reflective film may be deposited on the other cleavage surface.

FIG. 4(a) is a graph showing optical spectra measured while increasing the power applied to the thin film heater in the tunable DFB laser diode integrated with the thin film heater shown in FIGS. 2(a) to 2(c).

Referring to FIG. 4(a), in the thin film heater integrated tunable DFB laser diode 100 of the comparative example shown in FIGS. 2(a) to 2(c), as the power applied to the thin film heater 10 increases, Accordingly, it can be seen that as the oscillation wavelength transitions to a longer wavelength, the light intensity of the side mode increases.

Figure 4(b) is a measurement taken while increasing the power applied to the thin film heater in the tunable DFB laser diode integrated with a thin film heater according to the embodiment shown in Figures 3(a) to 3(b), which is an embodiment of the present invention. This is a graph showing light spectra.

Referring to FIG. 4(b), in the thin film heater integrated tunable DFB laser diode 200 according to the embodiment shown in FIGS. 3(a) to 3(b), the power applied to the thin film heater 10 is It can be seen that the oscillation wavelength transitions to a longer wavelength as it increases, but the light intensity of the side mode does not increase significantly.

Figure 4(c) shows the thin film heater integrated tunable DFB laser diode shown in Figures 2(a) to 2(c) and the embodiment of the present invention shown in Figures 3(a) to 3(b). This is a graph showing the side mode suppression ratio (SMSR) according to the power applied to the thin film heater in the thin film heater integrated tunable DFB laser diode.

Referring to FIG. 4(c), in the thin film heater integrated tunable DFB laser diode 100 of the comparative example shown in FIGS. 2(a) to 2(c), as the power applied to the thin film heater 10 increases, the It can be seen that the value of the mode suppression ratio (SMSR) drops rapidly. On the other hand, in the thin film heater integrated tunable DFB laser diode 200 according to the embodiment shown in FIGS. 3(a) to 3(b), it can be confirmed that the value of the side mode suppression ratio (SMSR) is well maintained at 50 dB or more. You can.

Figure 5 is a plan view of a tunable DFB laser diode integrated with a thin film heater according to another embodiment of the present invention, and in particular, a plan view of a tunable DFB laser diode integrated with a thin film heater having a tapered line width. In describing FIG. 5 , components that are the same or similar to those of the embodiment disclosed in FIGS. 3 (a) to 3 (b) will be assigned the same reference numerals, and detailed description thereof will be omitted.

Referring to FIG. 5, in the thin film heater integrated tunable DFB laser diode 200' according to this embodiment, the line width of the thin film heater heating area 1 is wide at the central point 0 of the DFB laser diode 200'. It is tapered to gradually become narrower toward the cleavage surfaces at both ends. That is, the line width of the thin film heater heating area 1 is wide at the center (0) of the diffraction grating 4 and is tapered to decrease as it moves away from the center of the diffraction grating 40. According to the thin film heater integrated tunable DFB laser diode 200' according to this embodiment, the temperature distribution within the diffraction grating 4 in the resonance direction (X-X' direction) can be made more uniform.

Figure 6 is a cross-sectional view in the resonance direction of a tunable DFB laser diode integrated with a thin film heater according to another embodiment of the present invention, and in particular, a cross-sectional view in the resonance direction of a tunable DFB laser diode integrated with a thin film heater in which a single semiconductor optical amplifier is integrated. In describing FIG. 6, the same or similar components as those of FIGS. 1 to 3(b) and 5 are assigned the same reference numerals, and detailed descriptions thereof will be omitted.

Referring to FIG. 6, the thin film heater integrated tunable DFB laser diode 300 according to the present embodiment uses additional semiconductor light to increase the single mode output light intensity generated from the thin film heater integrated DFB laser diode unit 70. It is composed of a single integrated amplifier (80). According to the embodiment, in order to independently control the injection current of the thin film heater integrated DFB laser diode unit 70 and the semiconductor optical amplifier 80, the p ⁺ -InGaAs ohmic layer 24 is separated, and the thin film heater integrated The upper electrode 25 of the DFB laser diode unit 70 and the upper electrode 29 of the semiconductor optical amplifier 80 can be separated. Additionally, depending on the embodiment, an insulating trench or ion implantation region 28 may be formed in the upper clad layer 23 between the thin film heater integrated tunable DFB laser diode unit 70 and the semiconductor optical amplifier 80. Accordingly, an insulating trench or an ion implantation region (28) is additionally formed between the thin film heater integrated tunable DFB laser diode unit (70) and the separated ohmic layer (24) and upper electrodes (25, 29) of the semiconductor optical amplifier (80). ) is disposed, the upper electrode 25 of the thin film heater integrated DFB laser diode unit 70 and the upper electrode 29 of the semiconductor optical amplifier 80 can be more stably insulated.

Figure 7 is a cross-sectional view in the resonance direction of a tunable DFB laser diode integrated with a thin film heater according to another embodiment of the present invention, in particular, a single integrated field absorption optical modulator. This is a cross-sectional view in the resonance direction of a thin-film heater integrated tunable DFB laser diode. In describing FIG. 7, components that are the same or similar to those of the embodiment disclosed in FIG. 6 will be assigned the same reference numerals, and detailed description thereof will be omitted.

Referring to FIG. 7, the thin film heater integrated tunable DFB laser diode 400 according to the present embodiment absorbs an electric field to modulate the intensity of single-mode output light generated from the thin film heater integrated tunable DFB laser diode unit 70. It is composed of a single integrated light modulator 90. Depending on the embodiment, the core layer 30 of the field absorption optical modulator 90 is an InGaAsP bulk layer or an InGaAsP/ InGaAsP layer whose bandgap wavelength is approximately 40 nm to 60 nm smaller than the active layer 5 of the tunable DFB laser diode unit 70. It can be composed of InGaAsP MQW layers.

A single integrated field absorption optical modulator (90) When manufacturing a thin-film heater integrated tunable DFB laser diode (400), the active layer (5) is selectively removed using photo lithography and dry etching or wet etching, and then the core layer (30) of the field absorption light modulator (90) is removed. They can be joined in a butt-joint manner using a regrowth process. According to the embodiment, in order to independently control the thin film heater integrated tunable DFB laser diode unit 70 and the electric field absorption optical modulator 90, the p ⁺ -InGaAs ohmic layer 24 is separated, and the thin film heater integrated The upper electrode 25 of the tunable DFB laser diode unit 70 and the upper electrode 31 of the field absorption optical modulator 90 can be separated. In addition, depending on the embodiment, an insulating trench or ion implantation region 28 is formed in the upper clad layer 23 between the thin film heater integrated tunable DFB laser diode unit 70 and the field absorption optical modulator 90, thereby forming the thin film. The upper electrode 25 of the heater integrated DFB laser diode unit 70 and the upper electrode 31 of the field absorption optical modulator 90 can be more stably insulated.

Depending on the embodiment, the core layer 30 of the field absorption optical modulator 90 shown in FIG. 7 can integrate a passive waveguide layer by growing InGaAsP having a bandgap wavelength of 1.1 μm to 1.42 μm. Additionally, instead of the field absorption optical modulator 90, a Mach-Zehnder interferometer type optical modulator may be integrated into the thin film heater integrated DFB laser diode unit 70.

Figure 8(a) is a plan view of the resonance direction of a tunable DFB laser diode integrated with a thin film heater according to another embodiment of the present invention. In particular, it is a plan view of the tunable DFB laser diode integrated with a ridge-type thin film heater having a ridge-type waveguide structure. And, FIG. 8(b) is a vertical cross-sectional view of the ridge-type thin film heater integrated tunable DFB laser diode shown in FIG. 8(a), and is a cross-sectional view along the Y-Y' direction of FIG. 8(a). In describing FIGS. 8(a) to 8(b), the same or similar components as those in FIGS. 2(a) to 3(b) are assigned the same reference numerals, and detailed description thereof will be omitted. .

8(a) to 8(b), in the thin film heater integrated tunable DFB laser diode 500 according to this embodiment, the length of the thin film heater heating region 1 is that of the diffraction grating region 510. The embodiment disclosed in FIGS. 3(a) to 3(b) is formed to be longer than or equal to a length, and both ends of the diffraction grating region 510 are located inside the both ends of the thin film heater heating region 1 based on the cleavage plane. It is configured in the same way as. However, the thin film heater integrated tunable DFB laser diode 500 according to this embodiment has a ridge-type waveguide 520, and the thin film heater heating area 1 is located on one side of the bottom of the ridge-type waveguide 520.

The ridge-type waveguide 520 structure has a simpler manufacturing process compared to the embedded structure, making it advantageous for low cost. However, considering overall characteristics such as threshold voltage, operating power, and temperature characteristics in addition to manufacturing cost, a buried or ridge-type waveguide structure may be selectively applied.

Although the technical idea of the present invention has been described in detail according to the above-described embodiments, it should be noted that the above embodiments are for explanation and not limitation. Additionally, those skilled in the art will understand that various modifications are possible within the scope of the technical idea of the present invention.

1: Thin film heater heating area 2: Thin film heater bridge
3: Thin film heater pad 4: Diffraction grating
5: Active layer 7, 8: Anti-reflective thin film
10: thin film heater 20: laser diode lower electrode
21: substrate 22, 22a, 22b: lower clad layer
23: upper clad layer 24: ohmic layer
25: laser diode upper electrode 26: insulating layer
27: Current blocking layer 28: Insulating trench or ion implantation area
29: Upper electrode of semiconductor optical amplifier 30: Core layer of field absorption optical modulator
31: Upper electrode of electric field absorption optical modulator 40, 50, 510: Diffraction grating area
60: Active waveguide area 70: DFB laser diode section
80: Semiconductor optical amplifier 90: Field absorption optical modulator
100, 200, 300, 400, 500: Thin film heater integrated tunable DFB laser diode
520: Ridge waveguide

Claims (16)

substrate,
A lower clad layer, a diffraction grating, an active layer, an upper clad layer, an ohmic layer, an upper electrode, and an insulating layer stacked on the substrate;
It includes a thin film heater having a heating area located on the insulating layer,
A thin film heater integrated tunable distribution feedback laser diode, characterized in that the length of the heating area of the thin film heater is smaller than the length of the active layer waveguide in the resonance direction and is longer than the length of the diffraction grating area where the diffraction grating is disposed. According to paragraph 1,
The thin film heater is a thin film heater integrated tunable distributed feedback laser diode, characterized in that it further includes a thin film heater bridge connected to both ends of the heating region within the length of the active layer waveguide on the insulating layer. According to paragraph 1,
A thin film heater integrated tunable distribution feedback laser diode, characterized in that the line width of the heating area of the thin film heater is uniform in the resonance direction, which is the direction in which the active layer waveguide extends. According to paragraph 1,
A thin film heater integrated tunable distributed feedback laser diode, characterized in that the line width of the heating area of the thin film heater is tapered on the diffraction grating area. According to clause 4,
A thin film heater integrated tunable distributed feedback laser diode, characterized in that the line width of the heating area of the thin film heater is tapered in a manner that the line width decreases from the center to both sides of the diffraction grating. According to any one of claims 1 to 5,
A thin film heater integrated tunable distributed feedback laser diode, characterized in that the diffraction grating is located in the lower clad layer, the active layer, or the upper clad layer. According to any one of claims 1 to 5,
The diffraction grating is a thin film heater integrated tunable distributed feedback laser diode, characterized in that one of a λ/4 phase shift diffraction grating, a loss-coupled diffraction grating, a gain-coupled diffraction grating, and an index-coupled diffraction grating. According to any one of claims 1 to 5,
The thin film heater is a single thin film or one or more composites containing at least one of chromium (Cr), gold (Au), titanium (Ti), platinum (Pt), nickel (Ni), aluminum (Al), and silver (Ag). A thin-film heater integrated tunable distributed feedback laser diode, characterized in that it is formed in layers. According to any one of claims 1 to 5,
A thin film heater integrated tunable distribution feedback laser diode further comprising an anti-reflective film formed on both ends of the laser diode. According to any one of claims 1 to 5,
A thin film heater integrated tunable distribution feedback laser diode further comprising an anti-reflective film formed on one end of the cleavage surface of the laser diode and a highly reflective film formed on the other end of the cleavage surface. According to any one of claims 1 to 5,
The insulating layer is composed of a silicon oxide layer (SiO2) or a silicon nitride layer (SiNx) interposed between the upper electrode and the thin film heater to electrically insulate the upper electrode and the thin film heater. Integrated tunable distributed feedback laser diode. According to any one of claims 1 to 5,
A thin film heater integrated tunable distribution feedback laser diode, characterized in that the active layer is composed of a bulk layer of InGaAsP, InGaAlAs, InGaNAs or a multi-quantum well. According to any one of claims 1 to 5,
A thin film heater integrated tunable distribution feedback laser diode, characterized in that at least one of a semiconductor optical amplifier, a field absorption optical modulator, and a Mach-Zehnder optical modulator is integrated into the laser diode. According to clause 13,
A thin-film heater integrated tunable distributed feedback laser diode, characterized in that the ohmic layer and upper electrode of the laser diode and the semiconductor optical amplifier or the optical modulator are separated. According to clause 14,
A thin film heater integrated tunable distributed feedback laser diode, characterized in that an insulating trench or ion implantation region is additionally formed between the laser diode and the separated ohmic layer and upper electrode of the semiconductor optical amplifier or optical modulator. According to any one of claims 1 to 5,
A thin film heater integrated tunable distributed feedback laser diode, characterized in that the laser diode has a ridge-shaped waveguide, and the heating area of the thin film heater is located on one side of the bottom of the ridge-shaped waveguide.

Images