Pulse power supply for two-dimensional photonic crystal laser

Abstract

A pulse power supply (10) for a two-dimensional photonic crystal laser is a power supply that supplies a pulsed current to a two-dimensional photonic crystal laser (90), said power supply comprising: a continuous current source (11); a switching element group (12) in which a plurality of switching elements (12-k) are connected in parallel, the switching elements switching between a conductive state and a non-conductive state of current in accordance with a control electric signal that is input and cut off from the outside; a connection circuit (13) that connects the continuous current source (11), the switching element group (12), and the two-dimensional photonic crystal laser (90) in series; and a control electric signal source (14) that simultaneously inputs and cuts off the control electric signal to each of the plurality of switching elements (12-k).

Description

Pulse power supply for two-dimensional photonic crystal laser

[0001] The present invention relates to a pulse power supply for generating pulsed laser oscillation from a two-dimensional photonic crystal laser.

[0002] Conventionally, a workpiece has been subjected to machining, such as cutting, by irradiating the workpiece with a laser beam. In this case, repeated irradiation with a pulsed laser beam (pulse laser beam) rather than continuous irradiation with the laser beam over time allows for instantaneous irradiation of a high-power laser beam while reducing the amount of power input over the entire machining time, thereby enabling high-precision machining while preventing damage to the workpiece due to heat generation.

[0003] Patent Document 1 describes a two-dimensional photonic crystal laser capable of repeatedly emitting pulsed laser light. This two-dimensional photonic crystal laser includes an active layer, a two-dimensional photonic crystal layer, and an electrode for injecting current into the active layer. The two-dimensional photonic crystal layer has a structure in which regions (typically holes) with a refractive index different from that of the base material are arranged at a predetermined period within a plate-shaped base material. In this two-dimensional photonic crystal laser, light within a predetermined frequency band is generated in the active layer by supplying current from a power source through the electrode. Of the light within this frequency band, light with a frequency determined by the period resonates within the two-dimensional photonic crystal layer, is amplified, and then emitted. At this time, pulsed laser light is repeatedly emitted by repeatedly switching the current supplied from the power source on and off.

[0004] Japanese Patent Application Laid-Open No. 2018-144664

[0005] A power source called a pulse generator is used to supply current to the active layer of a two-dimensional photonic crystal laser. When the pulse width is from a few nanoseconds (ns) to several hundred ns, the maximum current that can be supplied from this pulse generator is several tens of amperes. However, to obtain high-power pulsed laser light with an instantaneous output of several hundred watts to one thousand watts, a pulse current source is required that can instantaneously supply a large current of, for example, 100 A or more with a pulse width similar to that described above.

[0006] The problem to be solved by the present invention is to provide a pulsed power supply capable of supplying a large pulsed current to a two-dimensional photonic crystal laser.

[0007] The pulse power supply for a two-dimensional photonic crystal laser according to the present invention, which has been made to solve the above problems, is a power supply that supplies a pulsed current to a two-dimensional photonic crystal laser, and is characterized by comprising: a) a continuous current source; b) a switching element group in which a plurality of switching elements are connected in parallel, each switching between a conductive state and a non-conductive state according to a control electrical signal that is input and cut off from the outside; c) a connection circuit that connects the continuous current source, the switching element group, and the two-dimensional photonic crystal laser in series; and d) a control electrical signal source that inputs and cuts off the control electrical signal to each of the plurality of switching elements simultaneously.

[0008] The switching element may be, for example, a field effect transistor (FET) or a bipolar transistor.

[0009] The order in which the continuous current source, the switching element group, and the two-dimensional photonic crystal laser are arranged in the connection circuit is not limited to this order and may be any order.

[0010] The continuous current source in the pulsed power supply for a two-dimensional photonic crystal laser according to the present invention (hereinafter abbreviated as "pulsed power supply") refers to a power supply capable of outputting a current for a period longer than the pulse width of the pulsed current generated by the pulsed power supply. The continuous current source may literally output a current continuously, like a DC power supply, or may be a capacitor or the like capable of releasing accumulated charge for a period longer than the pulse width of the pulsed current.

[0011] When an electric control signal is input from the electric control signal source to each of the plurality of switching elements, the plurality of switching elements simultaneously enter a conductive state. As a result, current supplied from the continuous current source flows through the two-dimensional photonic crystal laser and the plurality of switching elements. From this state, when the electric control signals input to the plurality of switching elements are simultaneously cut off, the plurality of switching elements simultaneously enter a non-conductive state. As a result, current supplied from the continuous current source does not flow through the two-dimensional photonic crystal laser or the plurality of switching elements. Through the above operation, the pulsed power supply according to the present invention supplies one pulse of current to the two-dimensional photonic crystal laser. Furthermore, by repeating the above operation, the pulsed power supply according to the present invention repeatedly supplies pulsed current to the two-dimensional photonic crystal laser. Note that, depending on the application, instead of repeatedly supplying pulsed current, only one pulse of current may be supplied to the two-dimensional photonic crystal laser.

[0012] In the above explanation, the switching element is said to be in a conductive state when an electric control signal is input and in a non-conductive state when the electric control signal is interrupted, but some types of switching elements are in a conductive state when the electric control signal is interrupted and in a non-conductive state when the electric control signal is input. The use of such switching elements is also included in the present invention.

[0013] Generally, a switching element has an upper limit to the amount of current that can be conducted. In the pulse power supply according to the present invention, by simultaneously conducting multiple switching elements connected in parallel, the maximum current that can be passed when the elements are conducting is the product of the upper limit of the current per switching element and the number of switching elements. This makes it possible to supply a large pulsed current to the two-dimensional photonic crystal laser.

[0014] A general pulse generator, gate driver IC, or the like can be used as the control electrical signal source.

[0015] While various switching elements (including Si-MOSFETs and SiC-MOSFETs, discussed below) can be used, it is preferable to use GaN-FETs, which use GaN as the semiconductor for the FET channel. GaN-FETs use the two-dimensional electron gas formed at the heterointerface between AlGaN and GaN as the channel. GaN-FETs have the advantage of better switching characteristics (the speed at which current is switched on / off) and on-resistance (electrical resistance when conducting) (i.e., faster switching and lower on-resistance) than the widely used Si-MOSFETs and the SiC-MOSFETs, which have recently become more popular as switching elements with higher performance than Si-MOSFETs. Instead of GaN-FETs, GaN-MOSFETs and GaN-MISFETs, which use GaN as the channel semiconductor and oxide or other insulators as the insulating layer, may also be used.

[0016] The pulsed power supply for a two-dimensional photonic crystal laser according to the present invention may further comprise a laser installation substrate having: a conductive plate material that is connected to the continuous current source directly or via the group of switching elements; a covering material that is an insulating layer material that covers the surface of the conductive plate material and has electrical connection holes that are holes that pass through the layer material; and a conductive connecting member that is provided so as to fill the electrical connection holes.

[0017] In a pulsed power supply for a two-dimensional photonic crystal laser equipped with the laser mounting substrate, the two-dimensional photonic crystal laser is mounted on the surface of a covering material so that one of a pair of electrodes of the two-dimensional photonic crystal laser is electrically connected to the connecting member directly or via another conductive member (submount). This connects the one electrode to a continuous current source via a conductive plate or the like. The other electrode of the two-dimensional photonic crystal laser is connected to the continuous current source directly or via a switching element group using a conductor or the like.

[0018] By using such a laser installation substrate, one of the pair of electrodes of the two-dimensional photonic crystal is connected to a continuous current source by a conductive plate material, thereby reducing inductance compared to when the electrode and the continuous current source are connected using a conductor or the like.

[0019] The pulsed power supply for a two-dimensional photonic crystal laser having the laser installation substrate can further be configured to have connection electrodes, one for each of the plurality of switching elements, arranged on the surface of the covering material at equal intervals around the electrical connection holes and electrically connected to the corresponding switching elements.

[0020] By using such connection electrodes, the connection electrodes are arranged at equal intervals around the two-dimensional photonic crystal laser installed at the position of the electrical connection hole so that one electrode contacts the conductive plate material within the electrical connection hole.Therefore, by electrically connecting these connection electrodes to the other electrode of the two-dimensional photonic crystal laser with a conductor or the like, the current conducted through each switching element can be supplied to the other electrode in a positionally uniform manner.

[0021] The pulse power supply according to the present invention can supply a large pulsed current to a two-dimensional photonic crystal laser.

[0022] 1 is a circuit diagram showing an embodiment of a pulsed power supply (pulsed power supply for a two-dimensional photonic crystal laser) according to the present invention. FIG. 2 is a perspective view showing an example of a two-dimensional photonic crystal laser to which a pulsed current is supplied by the pulsed power supply of this embodiment. FIG. 3 is a top view of a two-dimensional photonic crystal layer of the two-dimensional photonic crystal laser shown in FIG. 2. FIG. 4 is a longitudinal sectional view (a) and a partially enlarged view (b) showing the mounted state of the pulsed power supply of this embodiment. FIG. 5 is a top view showing the mounted state of the pulsed power supply of this embodiment. FIG. 6 is a graph showing the results of measuring the waveform of a pulsed current injected into a two-dimensional photonic crystal laser for a plurality of examples in which the voltage output from the continuous current source is different in the pulsed power supply of this embodiment. FIG. 7 is a graph showing the results of measuring the waveform of a pulsed current injected into a two-dimensional photonic crystal laser for a plurality of examples in which the pulse width of the signal current output from the control electrical signal source is different in the pulsed power supply of this embodiment. FIG. 8 is a graph showing the results of measuring the time change in intensity of pulsed laser light emitted from a two-dimensional photonic crystal laser for a plurality of examples in which the pulse width of the signal current output from the control electrical signal source is different in the pulsed power supply of this embodiment. 12 is a graph showing the results of measuring the relationship between the magnitude of a pulse current repeatedly injected into a two-dimensional photonic crystal laser from the pulsed power supply of this embodiment and the output power of a pulsed laser beam emitted from the two-dimensional photonic crystal laser. Photographs of far-field patterns of pulsed laser beams emitted from the two-dimensional photonic crystal laser by repeatedly injecting a pulse current into the two-dimensional photonic crystal laser from the pulsed power supply of this embodiment, taken for the magnitudes of the pulsed current of (a) about 100 A, (b) about 700 A, and (c) about 1400 A. A schematic configuration diagram showing an example of a laser marking processing apparatus using a two-dimensional photonic crystal laser to which a pulsed current is supplied from the pulsed power supply of this embodiment. Photographs showing an example of processing the surface of a stainless steel plate material using the laser marking processing apparatus of the example of FIG. 11. A partially enlarged vertical cross-sectional view showing a modified example of the mounting state of the pulsed power supply of this embodiment. A partially enlarged vertical cross-sectional view showing another modified example of the mounting state of the pulsed power supply of this embodiment. A partially enlarged vertical cross-sectional view showing yet another modified example of the mounting state of the pulsed power supply of this embodiment. A partially enlarged vertical cross-sectional view showing a modified example having a plurality of laser mounting substrates.FIG. 10 is a longitudinal cross-sectional view showing a modified example in which switching elements are provided on both the upper and lower surfaces of a substrate.

[0023] 1 to 17, an embodiment of a pulse power supply for a two-dimensional photonic crystal laser (hereinafter abbreviated as "pulse power supply") according to the present invention will be described.

[0024] (1) Configuration of the Pulsed Power Supply of the Present Embodiment Fig. 1 shows a circuit diagram of a pulsed power supply 10 of the present embodiment. This pulsed power supply 10 is a power supply that supplies a pulsed current to a two-dimensional photonic crystal laser 90, and includes a continuous current source 11, a switching element group 12, a connection circuit 13, and a control electrical signal source 14.

[0025] The continuous current source 11 comprises a DC power supply 111 and a capacitor 112 connected in parallel to the DC power supply 111. This continuous current source 11 is a power supply that can output a current for a period longer than the width of the pulse current generated by the pulse power supply 10 by discharging the charge accumulated in the capacitor 112 from the DC power supply 111. By mounting the capacitor 112 on the laser installation board 15 and shortening the wiring distance between the switching element 12-k and the capacitor, it is possible to reduce inductance. It is preferable to use multiple capacitors with fast response speeds in order to pass a large current.

[0026] The switching element group 12 includes n (n is a natural number equal to or greater than 2) switching elements 12-1, 12-2, ..., 12-n (hereinafter, collectively referred to as "switching element 12-k") connected in parallel. In this embodiment, a GaN-FET is used for the switching element 12-k. In the example shown in FIG. 1, the drain electrodes of the GaN-FETs are connected in parallel to the positive electrode of the continuous current source 11 (via the two-dimensional photonic crystal laser 90) and the source electrodes are connected in parallel to the negative electrode of the continuous current source 11 by the connection circuit 13. In this example, the two-dimensional photonic crystal laser 90 is connected between the positive electrode of the continuous current source 11 and the switching element group 12; however, it may also be connected between the switching element group 12 and the negative electrode of the continuous current source 11.

[0027] Note that switching element 12-k may be an FET other than a GaN-FET, and furthermore, any switching element other than an FET may be used as long as it switches between a conductive state and a non-conductive state of current in response to a control electrical signal that is input and interrupted from the outside. However, it is preferable to use a GaN-FET as switching element 12-k as in this embodiment because of its fast switching speed and low on-resistance.

[0028] The control electrical signal source 14 repeatedly generates a pulsed signal voltage at a predetermined cycle. A normal pulse generator is used as this control electrical signal source 14. A gate driver IC or the like may be used instead of the pulse generator. The output of the control electrical signal source 14 is connected in parallel to the gate electrodes of each switching element 12-k.

[0029] Here, we will explain the two-dimensional photonic crystal laser 90 to which the pulsed current is supplied by the pulsed power supply 10. As shown in Figure 2, the two-dimensional photonic crystal laser 90 has a configuration in which an output electrode 971, a laser internal substrate 96, an n-type cladding layer 941, an active layer 91, a spacer layer 93, a two-dimensional photonic crystal layer 92, a p-type cladding layer 942, and a back electrode 972 are stacked in this order. However, the order of the active layer 91 and the two-dimensional photonic crystal layer 92 may be reversed. In Figure 2, the back electrode 972 is depicted separated from the p-type cladding layer 942 for illustrative purposes, but in reality it is in contact with the surface of the p-type cladding layer 942.

[0030] The laser internal substrate 96 and n-type cladding layer 941 are made of n-type semiconductors, while the p-type cladding layer 942, a base material 921 (described later) of the two-dimensional photonic crystal layer 92, and the spacer layer 93 are made of p-type semiconductors. The connection circuit 13 connects the emission side electrode 971 to the negative electrode of the continuous current source 11 via the switching element group 12, and the back side electrode 972 to the positive electrode of the continuous current source 11.

[0031] The active layer 91 emits light having a predetermined wavelength band when electric charges are injected by a current flowing between the emission electrode 971 and the back electrode 972. The material of the active layer 91 can be, for example, an InGaAs / AlGaAs multiple quantum well (emission wavelength band: 935 to 945 nm).

[0032] As described above, the two-dimensional photonic crystal layer 92 is formed by arranging modified refractive index portions 922, which have a refractive index different from that of the plate-shaped base material 921 made of a p-type semiconductor, periodically in a two-dimensional pattern ( FIG. 3 ). In this embodiment, the modified refractive index portions 922 made of voids (air) are arranged in a square lattice pattern, but the modified refractive index portions 922 may also be formed by embedding a member made of a material with a refractive index different from that of the base material 921 into the base material 921.

[0033] The output electrode 971 is made of a conductive plate material, and in its center, a window 9710 is formed, which is a portion where the plate material is not present. The window 9710 is provided to allow the laser beam generated within the two-dimensional photonic crystal laser 90 to pass through and be emitted outside the two-dimensional photonic crystal laser 90, as will be described later.

[0034] Next, the specific structure of the pulsed power supply 10 of this embodiment will be described with reference to Figures 4 and 5. The pulsed power supply 10 further includes a laser mounting substrate 15. The laser mounting substrate 15 has a three-layer structure consisting of, in order from the top, an insulating covering material 151, a conductive plate material 152, and an insulating support plate material 153. The covering material 151 covers the surface of the conductive plate material 152 and serves to electrically insulate the elements mounted on the top surface of the laser mounting substrate 15 (which is also the top surface of the covering material 151) from the conductive plate material 152. An electrical connection hole 1511 is provided near the center of the covering material 151 as viewed from the surface. The electrical connection hole 1511 is filled with a conductive connecting member 1512. The surface of the connecting member 1512 is exposed beyond the surface of the covering material 151 and extends outside the covering material 151. There may be provided one or more electrical connection holes 1511 and connection members 1512. When there are multiple connection members 1512, it is desirable that the multiple connection members 1512 are connected together on the surface.

[0035] The continuous current source 11 (not shown in FIG. 5) is disposed outside the laser mounting substrate 15, and its positive electrode is electrically connected to the conductive plate material 152. The negative electrode of the continuous current source 11 is connected in parallel to the source electrodes of each switching element 12-k mounted on the upper surface of the laser mounting substrate 15, as will be described later. The control electrical signal source 14 (not shown in FIGS. 4 and 5) is also disposed outside the laser mounting substrate 15, and is electrically connected to the gate electrodes of each switching element 12-k. The continuous current source 11 may be mounted on the laser mounting substrate 15.

[0036] Each switching element 12-k constituting the switching element group 12 is arranged on the upper surface of the laser installation substrate 15 at equal intervals (circumferentially) around an electrical connection hole 1511. An electrode pad (connection electrode) 154 is arranged between each switching element 12-k and the electrical connection hole 1511. These electrode pads 154 are also arranged at equal intervals around the electrical connection hole 1511. The drain electrode of each switching element 12-k is connected to the electrode pad 154 corresponding to that switching element 12-k by a switching element-to-pad conductor 155. The electrode pads 154 may be physically separated or connected as shown in FIG. 5, but are preferably arranged symmetrically with respect to the two-dimensional photonic crystal laser 90.

[0037] The two-dimensional photonic crystal laser 90 is placed on the upper surface of the laser installation substrate 15 so that the back electrode 972 is in contact with the connecting member 1512. Solder, a conductive adhesive, a sintered bonding material, or the like can be used to connect the back electrode 972 to the connecting member 1512. This electrically connects the back electrode 972 to the conductive plate 152 via the connecting member 1512.

[0038] Furthermore, the emission-side electrode 971 of the two-dimensional photonic crystal laser 90 is connected to each electrode pad 154 by an electrode-pad conductor 156. A flexible conductor is used for the electrode-pad conductor 156 to facilitate connection to the emission-side electrode 971. On the other hand, the switching element-pad conductor 155 does not need to be flexible, and a conductor such as a conductor wire or metal foil (e.g., copper foil) that is thicker and has lower electrical resistance than the electrode-pad conductor 156 is used. In order to pass a large current, it is preferable to provide multiple switching element-pad conductors 155 and electrode-pad conductors 156 per electrode pad 154 or to use wide, thick metal foil or the like to ensure a sufficient cross-sectional area.

[0039] (2) Operation of the Pulsed Power Supply of the Present Embodiment The operation of the pulsed power supply 10 of the present embodiment will be described. In the initial state, the control electrical signal source 14 does not output a signal voltage, and each of the switching elements 12-k constituting the switching element group 12 is in a non-conducting state. Therefore, no current is injected into the two-dimensional photonic crystal laser 90.

[0040] When pulsed power supply 10 starts operating by a predetermined operation, control electrical signal source 14 outputs a pulsed signal voltage for one pulse. The output signal voltage for one pulse is applied to the gate electrode of each switching element 12-k. As a result, each switching element 12-k simultaneously becomes conductive, and current supplied from continuous current source 11 flows between the drain electrode and the source electrode. This injects current into two-dimensional photonic crystal laser 90. Subsequently, when the application of this one-pulse signal voltage is stopped, each switching element 12-k simultaneously becomes non-conductive, and current stops flowing between the drain electrode and the source electrode. This also stops current flow in two-dimensional photonic crystal laser 90. Through the operations up to this point, one pulse of current is supplied from pulsed power supply 10 to two-dimensional photonic crystal laser 90. Then, by repeating these operations, pulsed current is repeatedly supplied from pulsed power supply 10 to two-dimensional photonic crystal laser 90. Note that instead of repeatedly supplying pulsed current, an operation of supplying only one pulse of current may be performed independently.

[0041] By supplying a pulsed current to two-dimensional photonic crystal laser 90 in this manner, pulsed light is emitted in a region (current injection region) of active layer 91 in two-dimensional photonic crystal laser 90 into which the current is injected. Of the light thus generated, pulsed light having a wavelength corresponding to the periodic length of the square lattice in which modified refractive index portions 922 are arranged is amplified in two-dimensional photonic crystal layer 92 and oscillates as a laser. This generates a pulsed laser beam, which is emitted to the outside from window 9710 of emission-side electrode 971.

[0042] When such a pulsed current is repeatedly supplied to two-dimensional photonic crystal laser 90, a pulsed laser beam is repeatedly emitted from two-dimensional photonic crystal laser 90.

[0043] In the pulsed power supply 10 of this embodiment, a switching element group 12 in which a plurality of switching elements 12-k are connected in parallel is used to generate a pulsed current from the current continuously supplied from the continuous current source 11, and since these switching elements 12-k are simultaneously in a conducting state, the maximum current that can flow when conducting is the product of the upper limit of the current that each switching element 12-k can conduct and the number of switching elements 12-k. As a result, the pulsed power supply 10 of this embodiment can supply a large pulsed current to the two-dimensional photonic crystal laser 90.

[0044] Furthermore, in the pulsed power supply 10 of this embodiment, the back electrode 972 of the two-dimensional photonic crystal laser 90 and the continuous current source 11 are electrically connected by the conductive plate material 152 of the laser installation substrate 15. This makes it possible to reduce inductance compared to when the back electrode 972 and the continuous current source 11 are connected by an ordinary conductor.

[0045] Furthermore, in pulsed power supply 10 of this embodiment, electrode pads 154 are arranged at equal intervals around two-dimensional photonic crystal laser 90 installed at the position of electrical connection hole 1511. Therefore, the current conducted through each switching element 12-k can be supplied positionally uniformly to output electrode 971 through each electrode pad 154. As a result, in two-dimensional photonic crystal laser 90, the current density in the current injection region of active layer 91 becomes uniform, and high-quality laser oscillation can be obtained.

[0046] (3) Experiments using the pulsed power supply of this embodiment The results of experiments using the pulsed power supply 10 of this embodiment are shown below. The number of switching elements 12-k in the fabricated pulsed power supply 10 was four. The two-dimensional photonic crystal laser 90 used had an emission-side electrode 971 and a back-side electrode 972 formed so that the current injection region in the active layer 91 was a circle with a diameter of approximately 3 mm.

[0047] For the fabricated pulsed power supply 10, a single pulse of pulsed signal voltage with a pulse width of 50 ns (nanoseconds) was supplied from the control electrical signal source 14 to each switching element 12-k, and the waveform of the pulsed current injected into the two-dimensional photonic crystal laser 90 was measured with an oscilloscope. This measurement was performed for several examples in which the DC voltage of the continuous current source 11 was different. The measurement results are shown in Figure 6. It was confirmed that a pulsed current with a pulse width of 50 ns, the same as the signal voltage, was injected into the two-dimensional photonic crystal laser 90. When the DC voltage of the continuous current source 11 was at its maximum, the magnitude of the pulsed current reached 1000 A, enabling the injection of a pulsed current in the kiloampere range.

[0048] Next, the waveform of the pulse current injected into the two-dimensional photonic crystal laser 90 for one pulse was measured with an oscilloscope for the cases where the signal voltage pulse width was shorter, 25 ns and 15 ns, while the same DC voltage as when the pulse current reached 1000 A in the measurement shown in Figure 6 was applied from the continuous current source 11. The pulse width of 15 ns is the lower limit of the pulse width of the pulsed signal voltage that can be generated by the pulse generator used as the control electrical signal source 14. The measurement results for these three cases (including an example where the signal voltage pulse width was 50 ns) are shown in Figure 7. It was confirmed that pulse currents having the same pulse widths of 25 ns and 15 ns as those signal voltages were injected into the two-dimensional photonic crystal laser 90 when the signal voltage pulse width was 25 ns and 15 ns, as in the case of 50 ns. Furthermore, the magnitude of the pulse current reached 1000 A in all cases.

[0049] Next, the temporal change in the intensity of the pulsed laser light emitted from the two-dimensional photonic crystal laser 90 was measured by injecting only one pulse of pulsed current under the same three conditions as in the measurement of Fig. 7. The results are shown in Fig. 8. It was confirmed that the two-dimensional photonic crystal laser 90 emitted a pulsed laser light having a pulse width corresponding to the pulsed current injected into it.

[0050] Next, an experiment was conducted in which a pulsed signal voltage with a pulse width of 50 ns was repeatedly supplied from control electrical signal source 14 to each switching element 12-k at a repetition rate of 100 Hz, and the output power of the pulsed laser light emitted from two-dimensional photonic crystal laser 90 was measured. This experiment was conducted for several examples in which different DC voltages were applied from continuous current source 11, thereby obtaining several sets of data showing different magnitudes of the pulsed current injected into two-dimensional photonic crystal laser 90. The measurement results are shown in Figure 9 as a graph with the magnitude of the pulsed current on the horizontal axis and the output power of the pulsed laser light on the vertical axis. It was confirmed that pulsed laser light can be repeatedly emitted with a maximum output power of kilowatts.

[0051] Figure 10 shows examples of far-field patterns of pulsed laser light obtained during the measurement shown in Figure 9. Figure 10 shows three examples where the magnitude of the pulse current is (a) approximately 100 A, (b) approximately 700 A, and (c) approximately 1400 A. In all cases, the divergence angle of the laser beam is less than 1°. For applications such as processing workpieces and distance measurement using laser light, it is necessary to make the divergence angle of the laser beam as small as possible, and laser beams with such small divergence angles of less than 1° are suitable for these applications. In the example (c), the divergence angle is approximately 0.23° and the brightness is approximately 1 GWcm. -2 sr -1 is.

[0052] (4) Example of Application to a Processing Apparatus The pulsed power supply 10 of this embodiment can be applied to various devices such as a processing apparatus and an optical communication device that use a two-dimensional photonic crystal laser 90. As one example of application, a laser marking processing apparatus will be described below.

[0053] The laser marking processing apparatus 20 is an apparatus that performs marking by irradiating a metal surface or the like with pulsed laser light. As shown in FIG. 11 , the laser marking processing apparatus 20 includes a sample stage 21, a stage drive source 22, a condenser lens 23, a two-dimensional photonic crystal laser 90, and a pulsed power supply 10. The sample stage 21 is a platform on which a workpiece W such as a metal plate is placed, and can be moved in two substantially horizontal directions (the X direction and the Y direction shown in FIG. 11 ) by operation of the stage drive source 22. The condenser lens 23 and the two-dimensional photonic crystal laser 90 are disposed above the sample stage 21. The two-dimensional photonic crystal laser 90 is disposed with its output electrode 971 (not shown in FIG. 11 ) facing downward. The condenser lens 23 is disposed between the sample stage 21 and the two-dimensional photonic crystal laser 90 and serves to focus the laser light emitted from the two-dimensional photonic crystal laser 90 on the surface of the workpiece W.

[0054] The operation of the laser marking processing apparatus 20 will now be described. With the workpiece W placed on the sample stage 21, a pulse current is supplied from the pulse power supply 10 to the two-dimensional photonic crystal laser 90, causing the two-dimensional photonic crystal laser 90 to irradiate the surface of the workpiece W with pulsed laser light. While irradiating the pulsed laser light in this manner, the sample stage 21 is moved in the X direction and / or Y direction by the stage drive source 22, thereby moving the position of the pulsed laser light relative to the workpiece W.

[0055] An oxide film is formed by irradiating a surface of stainless steel or the like with a laser beam. Then, by moving the pulsed laser beam so as to fill in a region R on the surface of the workpiece W, an oxide film is formed over a planar region on the surface of the workpiece W. The slower the moving speed of the pulsed laser beam (i.e., the longer the irradiation time at each position on the surface of the workpiece W), the thicker the oxide film formed on the surface of the workpiece W. When light is incident on the processed region R, light reflected from the surface of the oxide film and light reflected from the surface of the base material of the workpiece W (at the boundary with the oxide film) interfere with each other at specific wavelengths that satisfy the interference conditions. The wavelength of this interference light depends on the thickness of the oxide film, which in turn depends on the irradiation conditions of the pulsed laser beam used by the laser marking device 20. Therefore, the wavelength (color) of the light interfering in region R can be set by adjusting the moving speed of the pulsed laser beam. In this application example, the thickness of the oxide film is adjusted by the moving speed of the pulsed laser light, but it can also be adjusted in the same way by the optical output, pulse repetition frequency, pulse width, etc. of the pulsed laser light.

[0056] Figure 12 shows examples of irradiating a region (shown enclosed by a dashed line in the figure) on the surface of a workpiece made of a stainless steel plate with pulsed laser light using the laser marking device 20 for multiple examples of different pulsed laser light movement speeds. Due to electronic application regulations, color cannot be used in Figure 12 , but the color of the region changes as the pulsed laser light movement speed increases, i.e., as the oxide film formed by the laser marking device 20 becomes thinner. This corresponds to the change in the wavelength (color) of the light interfering in region R due to differences in oxide film thickness. Note that because the order of interference also changes depending on the oxide film thickness, the order of the pulsed laser light movement speed and the order of the wavelengths corresponding to the colors do not match.

[0057] As described above, the laser marking processing device 20 can be used to apply colored markings to the surface of a workpiece made of stainless steel or the like.

[0058] (5) Modifications The present invention is not limited to the above-described embodiment, and various modifications are possible.

[0059] For example, in the above embodiment, the connecting member 1512 of the laser installation substrate 15 is in direct contact with the backside electrode 972 of the two-dimensional photonic crystal laser 90, but as shown in FIG. 13 , a submount 161 made of a conductive material may be placed on the connecting member 1512, and the backside electrode 972 may be placed on the submount 161, thereby connecting the conductive plate material 152 and the backside electrode 972 via the connecting member 1512 and the submount 161.

[0060] 14 , a submount 162 may be used in which a first conductive portion 1621 made of a conductor is provided at a position corresponding to the connecting member 1512, a second conductive portion 1622 is provided at a position corresponding to the electrode pad 154, and the portion other than the first conductive portion 1621 and the second conductive portion 1622 is an insulating portion 1623 made of an insulator. This submount 162 is used by placing the first conductive portion 1621 and the connecting member 1512 and the second conductive portion 1622 so that they are in contact with each other, and by placing the back-side electrode 972 on the first conductive portion 1621 and connecting the second conductive portion 1622 and the emission-side electrode 971 with a conductor.

[0061] Instead of a flexible conductor, the emission-side electrode 971 and the electrode pad 154 may be connected using a non-flexible conductive connecting material 17 as shown in Fig. 15. In Fig. 15, the back-surface-side electrode 972 is in direct contact with the connecting member 1512, but the emission-side electrode 971 and the electrode pad 154 may be connected by a non-flexible connecting material 17 even when the submount 161 shown in Fig. 13 is used, and the emission-side electrode 971 and the second conductive portion 1622 may be connected by a non-flexible connecting material 17 even when the submount 162 shown in Fig. 14 is used.

[0062] As shown in FIG. 16 , a plurality of laser mounting boards 15 according to the above embodiment may be stacked vertically, electrically connecting the conductive plates 152 between adjacent laser mounting boards 15 with connecting members 1512 and electrically connecting the electrode pads 154, and mounting the two-dimensional photonic crystal laser 90 on the uppermost laser mounting board 15. In the example shown in FIG. 16 , a common electrode pad 154 is provided on each laser mounting board 15 so as to penetrate all the laser mounting boards 15 except for the lowermost laser mounting board 15. In this case, the side surfaces of the electrode pad 154 are covered with insulating material 1541 to prevent electrical contact between the electrode pad 154 and the conductive plates 152. Although three laser mounting boards 15 are used in FIG. 16 , the number of laser mounting boards 15 may be two, four, or more. By mounting the switching elements 12-k on each of the plurality of laser installation boards 15, the number of switching elements 12-k can be increased, and a pulse power supply with a higher output can be constructed.

[0063] As shown in FIG. 17 , switching elements 12-k connected to the power supply 11 may be provided not only on the mounting surface on which the two-dimensional photonic crystal laser 90 is mounted but also on the opposite surface (back surface) of the laser mounting substrate 15A. Here, the laser mounting substrate 15A is provided with covering materials 151A and 151B on both the front and back surfaces. In this case, electrode pads 154 are provided so as to penetrate the back surface of the laser mounting substrate 15A and reach the mounting surface. The sides of the electrode pads 154 are covered with insulating material 1541A to prevent electrical contact between the electrode pads 154 and the conductive plate 152. Each electrode pad 154 may be shared by both the mounting surface switching element 12-k and the back surface switching element 12-k (see FIG. 17 ). Alternatively, the electrode pads 154 for the back surface switching element 12-k may be provided separately from the electrode pads 154 for the mounting surface switching element 12-k. By providing the switching elements 12-k on both surfaces of the laser installation board 15A in this way, the number of switching elements 12-k can be increased, and a higher output pulse power supply can be configured. Also, a plurality of laser installation boards 15A having the switching elements 12-k on both surfaces (the mounting surface and the back surface) in this way may be stacked one on top of the other as in the example of FIG.

[0064] 16, multiple laser mounting substrates 15 are stacked one on top of the other, and two-dimensional photonic crystal laser 90 is mounted on the uppermost laser mounting substrate 15, but multiple laser mounting substrates 15 may be arranged horizontally while being oriented approximately vertically, and a mounting substrate may be placed on these laser mounting substrates 15, and two-dimensional photonic crystal laser 90 may be mounted on the mounting substrate. In this case, as in the example of Fig. 16, conductive plates 152 may be electrically connected to each other with connecting members 1512, and electrode pads 154 may be electrically connected to each other, but connecting members 1512 of each conductive plate 152 and back-side electrodes 972 may also be connected with conductors, and each electrode pad 154 and emission-side electrode 971 may also be connected with conductors.

[0065] 10... Pulse power supply 11... Continuous current source 111... DC power supply 112... Capacitor 12... Switching element group 12-1, 12-2, 12-n, 12-k... Switching element 13... Connection circuit 14... Control electrical signal source 15, 15A... Laser installation substrate 151, 151A, 151B... Covering material 1511... Electrical connection hole 1512... Connection member 152... Conductive plate material 153... Support plate material 154... Electrode pad 1541, 1541A... Insulating material 155... Switching element-pad conductor 156... Electrode-pad conductor 20... Laser marking processing device 21... Sample stage 22... Stage drive source 23... Condenser lens 90... Two-dimensional photonic crystal laser 91... Active layer 92... Two-dimensional photonic crystal layer 921... Base material 922: Modified refractive index portion 93: Spacer layer 941: N-type cladding layer 942: P-type cladding layer 96: Laser internal substrate 971: Emission side electrode 9710: Window 972: Rear side electrode

Claims

1. A power supply for supplying a pulsed current to a two-dimensional photonic crystal laser, comprising: a) a continuous current source; b) a switching element group in which a plurality of switching elements are connected in parallel, and which switch the current between a conductive state and a non-conductive state in response to control electrical signals that are input and cut off from the outside; c) a connection circuit that connects the continuous current source, the switching element group, and the two-dimensional photonic crystal laser in series; and d) a control electrical signal source that inputs and cuts off the control electrical signals to each of the plurality of switching elements simultaneously.

2. A pulse power supply for a two-dimensional photonic crystal laser according to claim 1, wherein the switching element is a GaN-FET.

3. A pulsed power supply for a two-dimensional photonic crystal laser according to claim 1 or 2, further comprising a laser installation substrate having: a conductive plate material that is connected to said continuous current source directly or via said group of switching elements; a covering material that is an insulating layer material that covers the surface of said conductive plate material and has electrical connection holes that are holes that pass through said layer material; and a conductive connecting member that is provided so as to fill said electrical connection holes.

4. The pulse power supply for a two-dimensional photonic crystal laser according to claim 3, characterized in that it comprises a plurality of said laser installation substrates.

5. A pulse power supply for a two-dimensional photonic crystal laser according to claim 3, characterized in that the switching elements are provided on both surfaces of the laser installation substrate.

6. A pulsed power supply for a two-dimensional photonic crystal laser as described in claim 3, further comprising connection electrodes, one for each of said plurality of switching elements, arranged on the surface of said covering material at equal intervals around said electrical connection holes and electrically connected to the corresponding switching element.

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