Optical element device

Abstract

This optical element device (10) comprises: an optical chip (11); a control unit (12); and a temperature adjustment element (13). The optical chip comprises an optical chip substrate (111) and an optical element (114) disposed on the optical chip substrate. The control unit comprises an amplification circuit. Light introduced into the optical element is absorbed by the optical element and a photocurrent is generated. The control unit generates a drive current on the basis of the photocurrent. The temperature adjustment element adjusts the temperature of the optical chip substrate on the basis of the drive current.　As a result of said configuration, the present invention can provide an optical element device in which the temperature of an optical chip comprising an optical element can be controlled by means of a simple configuration.

Description

Optical element device

[0001] The present invention relates to an optical element device capable of temperature adjustment.

[0002] In the midst of the increasing need to transmit and receive a large amount of data such as generated by AI, the speed and power consumption of optical transmitters and receivers using light are advancing. In addition, optical elements mounted with a laser as a light source and a modulator that modulates laser light to generate a signal on a silicon substrate have been studied. As modulators, for example, there are an electro-absorption modulator (EAM) that absorbs light by applying a voltage for modulation, a micro-ring modulator (MRM) that applies a voltage to a small ring to change the absorption wavelength peak of light for modulation, etc. In addition, there is a Mach-Zehnder modulator (MZ) that performs intensity modulation by using the interference of light that is phase-adjusted and bifurcated. These modulators have a pn junction, and when light is absorbed, the power of the output light decreases and can be modulated. Due to this light absorption accompanying the modulation, a photocurrent is generated. Similarly in a photoreceiver, a germanium photodetector (Ge Photo-Detector, PD) generates a photocurrent when it absorbs light.

[0003] Since the bandgap of these optical elements themselves decreases as the temperature rises, the temperature dependence of the element characteristics is large, and it is necessary to adjust the temperature. For example, as the temperature rises, the bandgap decreases and the absorption of long-wavelength light increases. In other words, at a predetermined wavelength, even if the optical element shows good characteristics before the temperature rises, the light absorption may increase due to the temperature rise, the insertion loss may increase, and the extinction ratio may also decrease substantially. As a result, the element characteristics deteriorate.

[0004] In addition, since the refractive index of the materials constituting the optical element and the optical waveguide also has temperature dependence, it is necessary to perform temperature adjustment in order to achieve optimal operation including those other than the modulator and the photoreceiver. Therefore, the intensity and wavelength of light are monitored and fed back for temperature adjustment. In addition, by arranging a micro-heater near the optical element for temperature adjustment, the temperature can be adjusted locally.

[0005] T. Hiraki et al., “Over-67-GHz-Bandwidth Membrane InGaAlAs Electro-Absorption Modulator Integrated with DFB Laser on Si Platform,” Journal of Lightwave Technology, vol. 41, No. 3, 2023. S. Moazeni et al., “A 40-Gb / s PAM-4 Transmitter Based on a Ring-Resonator Optical DAC in 45-nm SOI CMOS,” IEEE Journal of Solid-State Circuits, vol. 52, No. 12, 2017.

[0006] In controlling the temperature of the optical elements described above, from the perspective of the mounting form, pluggable transceivers and the like have space for Peltier elements or heat sinks, making temperature control relatively easy. On the other hand, in co-packages and the like, which have seen increased demand in recent years, the optical elements are located near LSIs such as CPUs and GPUs. These LSIs have high power consumption and their operating states change rapidly. Furthermore, the optical elements and LSIs are mounted at high density. As a result, there has been a problem in that temperature control of the optical elements becomes difficult.

[0007] Furthermore, when implementing the temperature control described above, it is necessary to convert the light intensity and wavelength into electrical signals using a photodetector in order to monitor them. As a result, there was a problem of increasing the number of elements mounted on the chip.

[0008] Furthermore, while locally adjusting the temperature with a microheater can reduce power consumption, it also presents the problem that the optical elements become unpredictable due to the influence of ambient temperature conditions. In particular, when multiple optical elements are mounted on a chip or when the external temperature environment changes, thermal interference between adjacent elements complicates the control of the elements, or differences in the temporal response occur because the heat conduction state between elements placed around the chip and elements placed in the center of the chip differs from that of elements placed in the center of the chip.

[0009] Furthermore, since current is passed through the microheater, there was a problem in that electrical noise affected the optical elements.

[0010] To solve the problems described above, the optical device according to the present invention comprises an optical chip, a control unit, and a temperature control element, wherein the optical chip comprises an optical chip substrate and an optical element disposed on the optical chip substrate, the control unit comprises an amplification circuit, light input to the optical element is absorbed by the optical element, a photocurrent is generated, the control unit generates a drive current based on the photocurrent, and the temperature control element adjusts the temperature of the optical chip substrate based on the drive current.

[0011] According to the present invention, it is possible to provide an optical element device that can control the temperature of an optical chip equipped with an optical element with a simple configuration.

[0012] Figure 1 is a schematic diagram showing the configuration of an optical element device according to the first embodiment of the present invention. Figure 2A is a diagram illustrating the operation of an optical element device according to the first embodiment of the present invention. Figure 2B is a diagram illustrating the operation of an optical element device according to the first embodiment of the present invention. Figure 2C is a diagram illustrating the operation of an optical element device according to the first embodiment of the present invention. Figure 2D is a diagram illustrating the operation of an optical element device according to the first embodiment of the present invention. Figure 3A is a schematic top view showing the configuration of an optical element device according to the second embodiment of the present invention. Figure 3B is a cross-sectional view III-IIIB' showing the configuration of an optical element device according to the second embodiment of the present invention. Figure 3C is a diagram illustrating the operation of an optical element device according to the second embodiment of the present invention. Figure 3D is a diagram illustrating the operation of an optical element device according to the second embodiment of the present invention. Figure 3E is a diagram illustrating the operation of an optical element device according to the second embodiment of the present invention. Figure 4A is a block diagram showing the configuration of the electrical circuit of an optical element device according to the third embodiment of the present invention. Figure 4B is a circuit diagram showing an example of the configuration of the electrical circuit of an optical element device according to the third embodiment of the present invention. Figure 4C is a circuit diagram showing an example of the configuration of an electrical circuit for an optical element device according to the third embodiment of the present invention. Figure 5A is a block diagram showing the configuration of an electrical circuit for an optical element device according to the fourth embodiment of the present invention. Figure 5B is a circuit diagram showing an example of the configuration of an electrical circuit for an optical element device according to the fourth embodiment of the present invention. Figure 5C is a circuit diagram showing an example of the configuration of an electrical circuit for an optical element device according to the fourth embodiment of the present invention. Figure 6A is a block diagram showing the configuration of an electrical circuit for an optical element device according to the fifth embodiment of the present invention. Figure 6B is a circuit diagram showing an example of the configuration of an electrical circuit for an optical element device according to the fifth embodiment of the present invention. Figure 6C is a circuit diagram showing an example of the configuration of an electrical circuit for an optical element device according to the fifth embodiment of the present invention. Figure 6D is a block diagram showing the configuration of an electrical circuit for an optical element device according to the fifth embodiment of the present invention. Figure 7A is a block diagram showing the configuration of an electrical circuit for an optical element device according to the sixth embodiment of the present invention. Figure 7B is a circuit diagram showing an example of the configuration of an electrical circuit for an optical element device according to the sixth embodiment of the present invention.Figure 7C is a diagram illustrating the operation of the electrical circuit of an optical element device according to the sixth embodiment of the present invention. Figure 7D is a diagram illustrating the operation of the electrical circuit of an optical element device according to the sixth embodiment of the present invention. Figure 8A is a schematic cross-sectional diagram showing an example of the configuration of an optical element device according to the seventh embodiment of the present invention. Figure 8B is a schematic cross-sectional diagram showing a part of an example of the configuration of an optical element device according to the seventh embodiment of the present invention. Figure 8C is a schematic cross-sectional diagram showing an example of the configuration of an optical element device according to the seventh embodiment of the present invention. Figure 8D is a schematic cross-sectional diagram showing an example of the configuration of an optical element device according to the seventh embodiment of the present invention. Figure 9 is a diagram showing an example of the configuration of a computer in an embodiment of the present invention.

[0013] <First Embodiment> An optical element device according to the first embodiment of the present invention will be described with reference to Figures 1 to 2D.

[0014] <Configuration of the Optical Device> As shown in Figure 1, the optical device 10 according to this embodiment comprises an optical chip 11, a control unit 12, and a temperature control element 13. The optical device 10 also comprises a module substrate 14.

[0015] The optical chip 11 comprises an optical device layer 112 on an optical chip substrate 111. The optical chip substrate 111 is, for example, Si.

[0016] The optical device layer 112 comprises an optical element 114 and an optical waveguide 113 optically connected to the optical element 114, wherein the optical element 114 and the optical waveguide 113 are connected to SiO ２ It has a configuration in which it is embedded with insulating material 115.

[0017] The optical element 114 is an element that operates based on light absorption and generates a photocurrent, such as an EAM or PD. The optical element 114 is made of a compound semiconductor such as InP. The optical waveguide 113 is made of a compound semiconductor such as Si or InP.

[0018] The optical chip 11 is mounted with the side facing the optical device layer 112 (front surface) facing the surface of the module substrate 14 (face down). The optical chip 11 may also be mounted with the side facing the optical chip substrate 111 (back surface) facing the surface of the module substrate 14 (face up).

[0019] The temperature control element 13 is a heater. Alternatively, it may be a Peltier element.

[0020] The optical chip 11, the control unit 12, and the heater 13 are electrically connected via the module board 14 and electrical wiring 15.

[0021] <Operation of the Optical Device> In the optical device 10, when input light 1 is input to the optical device 114 via the optical waveguide 113, the input light 1 is absorbed by the optical device 114. If the optical device 114 is an EAM, a portion of the input light 1 is absorbed, and if it is a PD, all of the input light 1 is absorbed. As a result, a photocurrent 3 is generated and taken out of the optical chip 11 via the electrical wiring 15.

[0022] If the optical element 114 is an EAM, the light that was not absorbed during modulation in the EAM is output as output light 2.

[0023] Next, the photocurrent 3 is input to the control unit 12. The control unit 12 processes the photocurrent 3 and outputs a drive current 4 according to the photocurrent 3.

[0024] Next, the drive current 4 is input to the temperature control element (heater) 13. The drive current 4 is converted into heat (shaded arrow in Figure 1) in the heater 13. The heat generated in the heater 13 is conducted to the optical chip substrate 111 of the optical chip 11. A portion of the heat conducted to the optical chip substrate 111 is conducted to the optical element 114, adjusting the temperature of the optical element 114. The heat that is not conducted to the optical element 114 is released to the outside of the optical element device 10.

[0025] <Effect> In the optical element device 10, for example, the size of the optical chip 11 is 1 mm wide × 3 mm long × 0.7 mm thick. The optical element 114 is formed in a region with a thickness of 10 μm from the surface (one side) of the optical chip 11.

[0026] In this configuration, the thermal capacity of the optical chip substrate 111, which is made of Si, is approximately 3.8 mW·s / K, and is mainly SiO ２ The thermal capacity of the optical device layer 112, which is composed of these materials, is 0.05 mW·s / K. The thermal capacity of the optical device layer 112 is about 1 / 75 of that of the optical chip substrate 111, and is therefore susceptible to temperature changes.

[0027] For example, when the LSI changes from an operating state to an idle (standby) state in the external environment of the optical device layer 112, and the temperature of the surrounding area including the optical element 114, LSI, and chip substrate 111 drops by 50°C in 10 seconds, the heating of the heater 13 at a rate of approximately 19 mW can maintain a constant temperature in the surrounding area including the optical element 114, LSI, and chip substrate 111.

[0028] In the conventional configuration, only the optical device layer 112 is locally heated by the microheater, and because the heat output of the microheater is small (0.25 mW), the temperature of the optical element 114 decreases due to the influence of the external environment (temperature). As a result, a delay of about 750 seconds occurs to recover the temperature.

[0029] In this configuration, when the temperature of the optical chip substrate 111 changes due to changes in the external environment temperature, the temperature of the optical device layer 112 also changes. As a result, the temperature is unevenly distributed within the plane of the optical device layer 112 of the optical chip substrate 111, the characteristics of the optical elements 114 change, and the characteristics of the optical elements 114 located at different positions within the optical device layer 112 are unevenly distributed. In particular, in a configuration in which multiple modulators are operated in parallel lanes, a problem arises in which the variation in characteristics between lanes increases.

[0030] Furthermore, in a configuration that combines modulated signals of different wavelengths, a problem arises in which the optical loss in the multiplexer increases because the temperature of the multiplexer is unevenly distributed across the plane.

[0031] Furthermore, in conventional configurations, the output light 2 is split and converted into an electrical signal for optical detection. Therefore, since a portion of the power of the output light 2 is used for optical detection, the loss of signal light increases. In addition, the number of detection elements such as tap PD increases.

[0032] Furthermore, the electrical wiring for the microheater is located near the optical element 114. The current flowing through this wiring can also be a source of noise, which is a problem.

[0033] Meanwhile, in the optical device 10, the optical chip substrate 111 is heated. The thermal conductivity of the silicon constituting the optical chip substrate 111 is 149 W / m·K, and the SiO of the optical device layer 112 ２Because it has higher thermal conductivity compared to other materials, it can improve in-plane temperature uniformity in a short time. As a result, in a configuration in which multiple optical elements 114 and optical circuits such as multiplexers and demultiplexers are arranged, a uniform temperature distribution can be achieved overall, thus maintaining the characteristics.

[0034] Furthermore, since the photocurrent in the optical element 114 that does not contribute to the optical signal is directly detected and the drive current 4 is supplied to the temperature control element 13 via the control unit 12, there is no loss of signal light.

[0035] Furthermore, since the photocurrent 3 detected directly from the optical element 114 is processed by the control unit 12, there is no need to add or arrange additional optical elements.

[0036] Furthermore, since the drive current 4 for the heater 13 is not supplied to the optical chip (optical element) 11 and only heat is transferred, electrical wiring is not placed near the optical element 114, and the effects of noise are suppressed.

[0037] Figures 2A to 2C show the changes in the band gap of the semiconductor constituting the optical element 114, the intensity of the output light 2 of the optical device layer 112 (output light intensity), and the photocurrent 3 of the optical element 114, respectively, in response to the temperature change of the optical element 114. Figure 2D shows the change in the temperature of the optical element 114 in response to a change in the external ambient temperature.

[0038] When the temperature of the optical element 114 rises, the band gap decreases (Figure 2A). Accordingly, the intensity of the output light 2 from the optical device layer 112 decreases (Figure 2B). This decrease in the intensity of the output light 2 is due to a portion of the input light 1 being absorbed by the optical element 114. As a result, the photocurrent 3 increases (Figure 2C).

[0039] In conventional optical device devices that do not have a temperature control mechanism, the temperature of the optical element 114 changes in accordance with changes in the temperature of the external environment (dashed line in Figure 2D).

[0040] On the other hand, in the optical element device 10 equipped with a temperature control mechanism, the temperature of the optical element 114 can be stabilized in response to changes in the temperature of the external environment (solid line in Figure 2D). For example, when the temperature of the optical element 114 decreases due to a decrease in the temperature of the external environment, a decrease in the photocurrent 3 is detected, as shown in Figure 2C. Therefore, the temperature of the optical element 114 can be stabilized by adjusting the drive current 4 so that the heat generated by the heater 13 increases.

[0041] In this configuration, when the optical device layer 112 includes a plurality of optical elements 114, since they are heated by a single heater, the temperature varies depending on the position of the elements. As a result, the temperature cannot be made constant among the plurality of optical elements 114, so it is affected by the external environmental temperature, but the temperature of the optical elements 114 can be stabilized compared to a configuration without a temperature adjustment mechanism (the dashed line in FIG. 2D). Examples of changes in the temperature of the external environment include, for example, when the ambient temperature changes between about 0°C and 50°C, or when the LSI itself changes within a range of about 100°C from the ambient temperature along with a change in the operating state of an LSI in the vicinity.

[0042] According to the present embodiment, a temperature adjustment element such as a heater can be controlled by a drive current generated based on a photocurrent to adjust the temperature of the chip substrate of the optical chip. Since the chip substrate is made of a material having a high thermal conductivity such as silicon and has a large heat capacity, the entire optical chip can be adjusted to a uniform temperature with a simple configuration compared to the case of locally heating an optical element. Also, temperature adjustment can be performed for an optical element device in which optical elements, LSIs, etc. are mounted at high density.

[0043] <Second Embodiment> An optical element device according to a second embodiment of the present invention will be described with reference to FIGS. 3A to E.

[0044] <Configuration of Optical Element Device> FIGS. 3A and B respectively show an upper surface schematic view and a cross-sectional view taken along IIIB - IIIB' of an example of the configuration of the optical chip 11 and the module substrate 14 in the optical element device 20 according to the present embodiment.

[0045] The optical device layer 112 of the optical chip 11 includes a plurality (four) of optical elements 114, a wavelength demultiplexer (DEMUX) 116, a wavelength multiplexer (MUX) 117, and optical waveguides 113 that optically connect the respective elements.

[0046] The optical chip 11 is connected to the module substrate 14 via electrical connection terminals 118.

[0047] In the optical chip 11, different wavelengths (for example, four wavelengths λ １ ~λ ４Multiple lights having ) are mixed to form an input light 1, which is input to a wavelength demultiplexer (DEMUX) 116 via an optical waveguide 113, where it is demultiplexed (wavelength separated) by wavelength, modulated by an optical element (modulator) 114, input to a wavelength multiplexer (MUX) 117, combined, and output as output light 2.

[0048] In the optical chip 11, the wavelength demultiplexer and wavelength multiplexer are temperature sensitive, so it is necessary to maintain a constant and uniform temperature throughout the entire optical chip 11.

[0049] <Effects> The effects of the optical element device 20 according to this embodiment will be explained with reference to Figures 3C to 3E.

[0050] Figure 3C shows the time-dependent changes in the external ambient temperature (dashed line in the figure) and the temperature of the optical element 114 (solid line in the figure). When adjusting the temperature of the optical chip substrate 111, it takes time for the temperature change of the external environment to be transmitted to the optical element 114, so there is a delay from immediately after the external ambient temperature rise until the photocurrent 3 increases. As a result, an overshoot occurs in the initial stages of temperature adjustment because the heater output is reduced in response to the detection of the increase in photocurrent 3. After the initial overshoot occurs, the temperature can be maintained at a constant level. A similar overshoot occurs when the external ambient temperature decreases.

[0051] For comparison, a configuration in which the temperature of each optical element is locally adjusted in an optical element device will be described. Figure 3D shows the change over time between the external ambient temperature (dashed line in the figure) and the temperature of the optical element in this configuration. As an example, the cases where the optical element is placed near the outer edge of the chip (solid line in the figure) and where it is placed in the center of the chip (dotted line in the figure) are shown. Also, the temperature of the optical element 114 when adjusting the temperature of the optical chip substrate 111 shown in Figure 3C is shown by a dashed line.

[0052] Optical elements near the outer edge of the chip are quickly affected by the external environment and therefore react rapidly to increases and decreases in the external temperature. Because the amount of heat generated by the heater is small due to localized heating, the decrease in the temperature of the optical elements is large in the undershoot in response to a decrease in the external temperature.

[0053] The optical element in the center of the chip is slow to respond to temperature increases and decreases in the external environment. Furthermore, when the external temperature rises, the temperature of the optical element in the center of the chip rises due to the influence of the overshoot of adjacent optical elements near the outer edge of the chip. Similarly, when the external temperature falls, although the amount of heat generated by the heater is small, the temperature increases due to the influence of adjacent optical elements near the outer edge of the chip. Therefore, the decrease in the undershoot of the temperature of the optical element in the center of the chip is smaller compared to that of adjacent optical elements near the outer edge of the chip.

[0054] Thus, compared to cases where the temperature of each optical element is adjusted locally (Figure 3D) or when the temperature of the optical chip substrate 111 is adjusted (Figure 3C), the range of temperature changes in response to temperature increases and decreases in the external environment increases overall. In addition, the response of each optical element is staggered in the time axis direction. As a result, the temperature of multiple optical elements becomes non-uniform among elements due to temperature changes in the external environment, and the performance of each element also becomes non-uniform. This degrades the overall performance of the optical chip 11.

[0055] On the other hand, in the optical element device 20 according to this embodiment, as described above, the temperature of the optical chip substrate 111 is adjusted, so temperature changes and time differences between elements in response to temperature increases and decreases in the external environment can be suppressed. As a result, the temperature difference among the multiple optical elements 114 can be reduced, the performance of each element can be made uniform, and the overall performance of the optical chip 11 can be improved.

[0056] In the optical element device 20 according to this embodiment, the reference temperature T1 may be set to a predetermined temperature. The reference temperature is a temperature that is maintained constant when the external environment is in a steady state, and may be, for example, the temperature when the external environment is low.

[0057] As an example, Figure 3E shows the change in temperature of the optical element 114 over time when the reference temperature (temperature at time zero in Figure 3E) T1 is set to a lower temperature than the reference temperature T0 shown in Figure 3C (solid line in the figure). The external ambient temperature (dashed line in the figure) and the temperature of the optical element 114 shown in Figure 3C (dotted line in the figure) are also shown.

[0058] When a reference temperature T1 is set, the peak temperature during overshoot when the temperature of the optical element 114 rises is reduced. As a result, when the temperature of the external environment changes, the temperature change ΔT1 of the optical element 114 at reference temperature T1 can be reduced compared to the temperature change ΔT0 of the optical element 114 at reference temperature T0. In this way, by adjusting the reference temperature, the effect of temperature changes on the optical element 114 can be further reduced.

[0059] According to this embodiment, in addition to the effects of the first embodiment, the effects of thermal interference between multiple optical elements within the optical chip can be suppressed, the performance of each element can be made uniform, and the overall performance of the optical chip can be improved.

[0060] <Third Embodiment> An optical element device according to the third embodiment of the present invention will be described with reference to Figures 4A to 4C.

[0061] <Configuration of the Optical Device> Figure 4A shows the configuration of the electrical circuit in the optical device 30 according to this embodiment. The electrical circuit consists of an optical element 114, a control unit 221, and a temperature control element (heater) 13. The other configurations are the same as in the first and second embodiments.

[0062] In the electrical circuit of the optical device 30, an amplification circuit is used in the control unit 221. In the electrical circuit, a portion of the input light 1 is converted into a photocurrent 3, and the photocurrent 3 is input to the amplification circuit 221, amplified, and becomes a drive current 4. The drive current 4 generates heat in the heater 13 and releases the heat.

[0063] Figure 4B shows an example of the electrical circuit configuration. The optical element 114 is modeled as a pn junction, and the photocurrent 3 is input to a bipolar amplifier 221 (transistor), which amplifies the current and supplies current to the heater 13. For example, when the photocurrent 3 is 1 mA, the amplification factor is 100, and the heater resistance is 10 Ω, (100 mA) ２ A heat generation of 0.1W can be obtained by multiplying by 10Ω.

[0064] To increase the amount of heat generated, the amplification circuit 221 may be constructed from multiple stages of transistors, as shown in Figure 4C. In the configuration shown in Figure 4C, the degree of freedom in circuit design can be improved by copying the photocurrent using the current mirror circuit 222.

[0065] According to this embodiment, similar to the first embodiment, the temperature of the optical chip substrate can be adjusted by controlling a temperature control element such as a heater with a drive current generated based on the photocurrent, and the entire optical chip can be adjusted to a uniform temperature with a simple configuration.

[0066] <Fourth Embodiment> An optical element device according to the fourth embodiment of the present invention will be described with reference to Figures 5A to 5C.

[0067] <Configuration of the Optical Device> Figure 5A shows the configuration of the electrical circuit in the optical device 40 according to this embodiment. The electrical circuit consists of an optical element 114, a control unit, and a temperature control element (heater) 13. The other configurations are the same as in the first and second embodiments.

[0068] In the electrical circuit of the optical element device 40, the control unit includes a low-pass filter 322 and an amplification circuit 321.

[0069] The optical element 114 is a modulator, and a high-speed modulation signal is applied to it, causing the photocurrent 3 to also have high-frequency components.

[0070] The low-pass filter 322 is placed after the optical element 114. This extracts only the low-frequency components from the modulated signal output from the modulator. The low-frequency components of the signal reflect the effects of temperature changes more than the high-frequency components.

[0071] Figure 5B shows an example of the configuration of a low-pass filter 322 and an amplifier circuit 321. For example, the low-pass filter 322 is composed of an RC circuit. This allows for the creation of a slow signal that responds to the time change of the external ambient temperature (several degrees Celsius / second).

[0072] Figure 5C shows another example of the configuration of the low-pass filter 322 and the amplification circuit 321_2. In this configuration, the current-to-voltage conversion circuit 323 is used to convert the photocurrent 3 into a voltage to drive the heater 13. This allows for adjustment of the drive current 4 with greater flexibility, rather than just a one-to-one relationship with the photocurrent.

[0073] According to this embodiment, in addition to the effects of the first to third embodiments, the influence of noise from high-frequency signals can be suppressed, and temperature control can be performed with high precision using low-frequency signals that respond to temperature changes.

[0074] <Fifth Embodiment> An optical element device according to the fifth embodiment of the present invention will be described with reference to Figures 6A to 6D.

[0075] <Configuration of the Optical Device> Figure 6A shows the configuration of the electrical circuit in the optical device 50 according to this embodiment. The electrical circuit consists of an optical element 114, a control unit, and a temperature control element (heater) 13. The other configurations are the same as in the first and second embodiments.

[0076] In the electrical circuit of the optical element device 50, the control unit includes a low-pass filter 422, a current weighting circuit 423, and an amplification circuit 421.

[0077] The current weighting circuit 423 is connected to the adjustment terminal 424 to adjust the degree of amplification. This allows a portion of the photocurrent 3 to be input to the amplification circuit for adjustment.

[0078] Figure 6B shows an example of the electrical circuit configuration of the optical element device 50. In this configuration, the resistance value can be reduced by adjusting the variable resistor 425 at the adjustment terminal 424. The photocurrent 3 can be branched and flowed to GND, reducing the current input to the transistor 221. This allows adjustment of the weighting ratio of the photocurrent 3 contributing to the drive current 4 of the heater 13.

[0079] In this way, in the current weighting circuit 423, the photocurrent output from the low-pass filter 422 is branched at a predetermined ratio according to the signal input from the adjustment terminal 424, with one branch being output to the amplification circuit and the other to GND.

[0080] Figure 6C shows an example of a circuit configuration in which N optical elements 114_1 to N are arranged. Each single-element circuit 47_1 to N, corresponding to each optical element 114_1 to N, comprises an optical element 114_1 to N, a low-pass filter 422_1 to N, and a current weighting circuit 423_1 to N. The current weighting circuits 423_1 to N are controlled by adjustment terminals 424_1 to N. The output currents from the multiple single-element circuits 47_1 to N are input to an amplification circuit 421 having multiple input terminals. This allows for control that reflects the balance and weighting of all optical elements, rather than controlling the overall temperature adjustment with a single optical element.

[0081] Figure 6D shows another example of the electrical circuit configuration of the optical element device 50. In this configuration, the functions of a low-pass filter, a current weighting circuit, and an amplification circuit are integrated into the microcontroller unit (MCU) 426. Specifically, the MCU 426 takes the photocurrent 3 from multiple optical elements 114_1 to N and the settings from the adjustment terminal 427 as input, and internally performs processing such as low-pass filtering, current-to-voltage conversion, analog-to-digital conversion, weighting, digital-to-analog conversion, and current amplification, and outputs a drive current 4 to drive the heater 13. This simplifies the circuit configuration and allows external control as needed via the adjustment terminal.

[0082] According to this embodiment, in addition to the effects of the first to fourth embodiments, the drive current of the temperature control element can be controlled with high precision.

[0083] <Sixth Embodiment> An optical element device according to the sixth embodiment of the present invention will be described with reference to Figures 7A to 7C.

[0084] <Configuration of the Optical Device> Figure 7A shows the configuration of the electrical circuit in the optical device 60 according to this embodiment. The electrical circuit consists of an optical element 514, a control unit, and a temperature control element (heater) 13. The other configurations are the same as in the first and second embodiments.

[0085] In the electrical circuit of the optical element device 60, the control unit includes a current calculation circuit 522 and an amplification circuit 521.

[0086] The optical element 514 is divided into regions and outputs multiple photocurrents 3. These multiple photocurrents 3_1 and 3_2 are input to the current calculation circuit 522, which calculates and outputs a current. This current is amplified and supplied to the heater 13.

[0087] Figure 7B shows an example of the specific configuration of the electrical circuit of the optical element device 60. The optical element 514, as an example, has region a (514_1) and region b (514_2) adjacent to region a (514_1).

[0088] <Operation of the Optical Device> In the electrical circuit of the optical device 60, when light is input to the optical device 514 via the optical waveguide 113, the area closer to the input side is designated as region a (514_1), and the area further from the input side is designated as region b (514_2). Photocurrents Ia (3_1) and Ib (3_2) are output from regions a and b respectively via electrodes a (119_1) and b (119_2). The current calculation circuit 522 calculates from the photocurrents Ia and Ib to drive the heater 13.

[0089] The operation of the electrical circuit of the optical element device 60 will be explained in detail with reference to Figures 7C and 7D.

[0090] Figure 7C shows the changes in photocurrents Ia and Ib in response to changes in the intensity of input light 1. When input light 1 changes due to changes in the temperature of the light source or changes over time, the absolute values ​​of photocurrents Ia and Ib change according to the change in the intensity of input light 1. In region a, the photocurrent Ia is located on the input side of the light, so light absorption is large and the photocurrent is also large. On the other hand, in region b, the light that has been absorbed in region a is input and absorbed, so the photocurrent Ib in region b is small.

[0091] Furthermore, when the intensity of input light 1 is high, the number of electron and hole carriers generated by light absorption in region a increases excessively, causing field shielding. As a result, light absorption in region a decreases, and the increase in photocurrent Ia tends to saturate. This decrease in light absorption in region a increases the intensity of light transmitted through region b, and the photocurrent Ib in region b increases.

[0092] Thus, when the intensity of the input light 1 changes due to temperature changes or changes over time, the amount of heat generated by the heater 13 also changes. Since this change in heat generation is not due to temperature changes in the external environment, it is desirable to avoid or suppress it.

[0093] Figure 7D shows the ratio of photocurrent Ia to photocurrent Ib (Ia / Ib) with respect to the change in intensity of input light 1. As shown, the amount of change in response to the change in intensity of input light 1 is suppressed when the ratio of photocurrent Ia to photocurrent Ib is set to Ia / Ib. Therefore, the influence of the change in intensity of the external light source is suppressed when the ratio of photocurrent Ia to photocurrent Ib is set to Ia / Ib.

[0094] Therefore, the ratio Ia / Ib of the photocurrents is calculated by the current calculation circuit 522, and the amplification circuit 521 is controlled based on Ia / Ib to supply a drive current 4 to the heater 13, thereby canceling the effects of fluctuations in the light source. For example, the drive current 4 may be generated based on a value obtained by multiplying the photocurrent Ia by the ratio Ia / Ib of the photocurrents, or the drive current 4 may be generated based on a value obtained by multiplying the sum of the photocurrents Ia and Ib by the ratio Ia / Ib of the photocurrents.

[0095] According to this embodiment, in addition to the effects of the first to third embodiments, it is possible to suppress influences other than temperature changes in the external environment and control the temperature with high precision.

[0096] <Seventh Embodiment> An optical element device according to the seventh embodiment of the present invention will be described with reference to Figures 8A to 8D.

[0097] <Configuration of the optical element device> The optical element device 70 according to this embodiment includes, as an example, an optical chip 11, a control unit 12, a temperature control element 13, and a module substrate 14, as shown in Figure 8A.

[0098] The control unit 12 is located inside the electrical chip 621. The electrical chip 621 is connected to the voltage source 623.

[0099] A chip resistor 63 is used as the temperature control element 13.

[0100] The module board 14 is equipped with an optical chip 11, an electrical chip 621, and a chip resistor 63.

[0101] The LSI 622 may be placed on the module board 14.

[0102] Furthermore, the lid 66 may be positioned to cover the optical chip 11, the electrical chip 621, the chip resistor 63, and the LSI 622.

[0103] A fiber array 68 for inputting and outputting light is connected to the optical chip 11.

[0104] An underfill 67 is placed on the side of the chip resistor 63 and the side of the optical chip substrate 111. The underfill 67 is made of a material with high thermal conductivity (for example, a resin with high thermal conductivity). For example, the thermal conductivity of the underfill 67 is 1.5 W / m·K, which is higher than the thermal conductivity of air (approximately 0.025 W / m·K). This improves heat conduction between the side of the chip resistor 63 and the optical chip substrate 111.

[0105] Figure 8B shows an enlarged cross-sectional view of the area around the optical chip substrate 111 and the chip resistor 63 in the optical element device 70. The chip resistor 63 and the optical chip 11 are also thermally connected by electrical wiring 651 and vias 652 located inside the module substrate 14. The electrical wiring 651 is connected to the electrical terminal 632 of the chip resistor 63 and is connected to the optical chip substrate 111 via metal pads (electrical connection terminals) 118.

[0106] In this configuration, the electrical terminals 632 of the chip resistor, the electrical wiring 651, the vias 652, and the metal pads (electrical connection terminals) 118 constitute a metal connection structure. The metal connection structure is made of a metal with high thermal conductivity (for example, copper).

[0107] In the optical element device 70, by making at least one of the underfill 67 and the metal connection structure from a material with high thermal conductivity, the thermal conduction between the optical chip substrate 111 and the chip resistor 63 can be improved.

[0108] The current flowing through the chip resistor 63 flows through a portion of the electrical wiring 651 and a portion of the via 652 via the shortest path from the current source 631 to GND, and therefore does not flow to the optical chip 11 (dotted arrow in the figure).

[0109] Meanwhile, the heat generated in the chip resistor 63 is supplied to the optical chip 11 through improved heat conduction via multiple layers of electrical wiring 651, vias 652, and metal pads (electrical connection terminals) 118. In the optical chip 11, vias 652_2 are arranged that penetrate the optical device layer 112 having the optical element 114 and reach the vicinity of the optical chip substrate 111. This allows heat to be supplied to the optical chip substrate 111 via the electrical wiring 651 within the optical chip substrate 111. In this way, the flow of current and heat can be separated and controlled between the optical chip substrate 111 and the chip resistor 63 in the optical element device 70. This suppresses the current flowing through the optical chip and reduces the influence of electrical noise.

[0110] Figure 8C shows another example of the configuration of the optical element device 70.

[0111] In the optical element device 70, a film resistor (film heater) 731 is used as the heater. The film resistor 731 is connected to the module board 14 via a connector terminal 733.

[0112] The connector terminals 733, LSI 622, electrical chip 621, and optical chip 11 are mounted on the module board 14 by reflow soldering.

[0113] The film resistor 731 is connected to the connector terminal 733.

[0114] A lid 66 is mounted on the module board 14 so as to cover the connector terminals 733, LSI 622, optical chip 11, film resistor 731, connector terminals 733, etc.

[0115] The film resistor 731 has a material with high thermal conductivity on one side (for example, the surface). For example, in the film resistor 731, one side has high thermal conductivity. By placing this side facing the optical chip substrate 111 and pressing it from above with the lid 66, the film resistor 731 and the optical chip substrate 111 can be brought into close contact, allowing heat to be conducted effectively.

[0116] The film resistor 731 is equipped with a material with low thermal conductivity on its other side (for example, the back surface). This prevents heat generated by the film resistor 731 from escaping to the outside through the lid 66. It also suppresses the effects of changes in the temperature of the external environment surrounding the lid 66.

[0117] This configuration includes cases where the other surface is made of a material with low thermal conductivity, or where a material with low thermal conductivity is placed on the other surface. For example, in a film resistor 731, the other surface is positioned facing the lid 66. An insulating layer 732 made of a material with high thermal insulation properties, such as sponge or rubber, is placed between this surface and the lid 66.

[0118] In the optical device 70, as shown in Figure 8D, the electrical chip 621 may be mounted on the back side (bottom side in the figure) of the module substrate 14. This shortens the connection wiring 651 between the electrical chip 621 and the optical chip 11, improving high-frequency signal characteristics. Furthermore, the connection wiring 651 allows the heat generated by the electrical chip 621 to flow to the optical chip 11 instead of the lid 66, reducing the amount of heat generated by the chip resistor 63 in the total heat generated by the optical device 70.

[0119] According to this embodiment, in addition to the effects of the first to third embodiments, the influence of electrical noise can be suppressed.

[0120] As shown in Figure 9, the control unit of the optical element device according to an embodiment of the present invention can be realized by a computer equipped with a CPU (Central Processing Unit) 80, a storage device (memory) 81, and an interface 82.

[0121] In the embodiments of the present invention, examples of the structure, dimensions, materials, etc. of each component in the configuration and manufacturing method of the optical element device are shown, but the invention is not limited to these examples. Any configuration that allows the optical element device to perform its function and produce the desired effect is acceptable.

[0122] It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations are possible within the technical concept of the present invention by those with ordinary skill in the art. For example, the sixth embodiment may be combined with the fourth, fifth, or seventh embodiment, or the fourth or fifth embodiment may be combined with the seventh embodiment.

[0123] Some or all of the embodiments described above, or examples thereof, may also be described as follows, but are not limited to these.

[0124] (Note 1) An optical element device comprising an optical chip, a control unit, and a temperature control element, wherein the optical chip comprises an optical chip substrate and an optical element disposed on the optical chip substrate, the control unit comprises an amplification circuit, light input to the optical element is absorbed by the optical element, a photocurrent is generated, the control unit generates a drive current based on the photocurrent, and the temperature control element adjusts the temperature of the optical chip substrate based on the drive current.

[0125] (Note 2) The optical element device according to Note 1, comprising a plurality of optical elements, an optical demultiplexer, and an optical multiplexer, wherein the plurality of optical elements each have different wavelengths, are demultiplexed into optical elements of each wavelength by the optical demultiplexer, input to the optical elements, output from the optical elements, and combined by the optical multiplexer.

[0126] (Note 3) The optical device according to Note 1 or Note 2, wherein the control unit further comprises a low-pass filter, and the low-pass filter allows only the low-frequency components of the photocurrent to pass through.

[0127] (Note 4) The optical device according to Note 3, wherein the control unit further comprises a current weighting circuit, a signal is input to the current weighting circuit, and the current weighting circuit branches the low-frequency components of the photocurrent output from the low-pass filter at a predetermined ratio according to the input signal and outputs them to the amplification circuit.

[0128] (Note 5) The optical device according to any one of Notes 1 to 4, wherein the control unit further comprises a current calculation circuit, the optical element has two regions, light is input to one of the two regions to generate a first photocurrent, light transmitted through one region is input to the other of the two regions to generate a second photocurrent, and the current calculation circuit controls the amplification circuit based on the ratio of the first photocurrent to the second photocurrent.

[0129] (Note 6) The optical element device according to any one of Notes 1 to 5, further comprising a module substrate, wherein the optical chip, the control unit, and the temperature control element are mounted on the module substrate, and the optical chip substrate and the temperature control element are thermally connected with a material with high thermal conductivity.

[0130] (Note 7) The optical element device according to Note 6, comprising a resin filled between the optical chip substrate and the temperature control element, and a metal connection structure, wherein the temperature control element is a chip resistor, and the metal connection structure comprises electrical terminals of the chip resistor, vias disposed in the module substrate, electrical wiring connected to the vias, and a metal pad connected to the optical chip substrate, wherein either the resin or the metal connection structure is made of the material with high thermal conductivity.

[0131] (Note 8) The optical element device according to Note 6, wherein the optical chip is, in order, equipped with the temperature control element and a lid, the temperature control element being a film heater, the film heater having a material with high thermal conductivity on one side and a material with low thermal conductivity on the other side, the one side being positioned on the optical chip substrate side and the other side being positioned on the lid side.

[0132] (Note 9) An optical element device according to any one of Notes 4 to 8, comprising a plurality of circuits in which the optical element, the low-pass filter, and the current weighting circuit are arranged, and the output of each of the plurality of circuits is input to the amplification circuit.

[0133] This invention can be applied to optical communication systems or optical communication devices.

[0134] 10 Optical element device 11 Optical chip 111 Optical chip substrate 114 Optical element 12 Control unit 13 Temperature control element

Claims

1. An optical element device comprising an optical chip, a control unit, and a temperature control element, wherein the optical chip comprises an optical chip substrate and an optical element disposed on the optical chip substrate, the control unit comprises an amplification circuit, light input to the optical element is absorbed by the optical element, a photocurrent is generated, the control unit generates a drive current based on the photocurrent, and the temperature control element adjusts the temperature of the optical chip substrate based on the drive current.

2. The optical element device according to claim 1, comprising a plurality of optical elements, an optical demultiplexer, and an optical multiplexer, wherein the plurality of light beams each have a different wavelength, the plurality of light beams are demultiplexed by the optical demultiplexer according to their wavelengths, input to the optical element, output from the optical element, and combined by the optical multiplexer.

3. The optical device according to claim 1 or 2, wherein the control unit further comprises a low-pass filter, and the low-pass filter allows only the low-frequency components of the photocurrent to pass through.

4. The optical device according to claim 3, wherein the control unit further comprises a current weighting circuit, a signal is input to the current weighting circuit, and the current weighting circuit branches the low-frequency components of the photocurrent output from the low-pass filter at a predetermined ratio according to the input signal and outputs them to the amplification circuit.

5. The optical device according to claim 1 or 2, wherein the control unit further comprises a current calculation circuit, the optical element has two regions, light is input to one of the two regions to generate a first photocurrent, light transmitted through the one region is input to the other of the two regions to generate a second photocurrent, and the current calculation circuit controls the amplification circuit based on the ratio of the first photocurrent to the second photocurrent.

6. The optical element device according to claim 1 or claim 2, further comprising a module substrate, wherein the optical chip, the control unit, and the temperature control element are mounted on the module substrate, and the optical chip substrate and the temperature control element are thermally connected by a material with high thermal conductivity.

7. The optical element device according to claim 6, comprising a resin filled between the optical chip substrate and the temperature control element, and a metal connection structure, wherein the temperature control element is a chip resistor, and the metal connection structure comprises an electrical terminal of the chip resistor, a via disposed in the module substrate, electrical wiring connected to the via, and a metal pad connected to the optical chip substrate, and at least one of the resin and the metal connection structure is made of a material with high thermal conductivity.

8. The optical element device according to claim 6, comprising, in order, the temperature control element and a lid on the optical chip, wherein the temperature control element is a film heater, the film heater has a material with high thermal conductivity on one side and a material with low thermal conductivity on the other side, the one side is positioned on the optical chip substrate side and the other side is positioned on the lid side.

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