Bandwidth improvement of a distributed feedback through-hole laser

Abstract

A laser-emitting device (101) comprises a housing (10) and first, second, and third through-hole connection leads (14) projecting from the housing (10). A proximal end section of each of the first to third through-hole connection leads (14) is located within the housing (10), and a distal end section of each of the first to third through-hole connection leads (14) is located outside the housing (10). The laser-emitting device (101) further comprises a laser diode (21) and a photodiode (20) located within the housing (10).The laser diode (21) comprises a cathode electrically connected to the proximal end section of the first through-hole connection (1) and an anode electrically connected to the proximal end section of the second through-hole connection (2). The photodiode (20) comprises a cathode electrically connected to the anode of the laser diode (21) and an anode electrically connected to the proximal end section of the third through-hole connection (3). The laser (101) emitting device further comprises a resistor (30) attached to an outer surface of the housing (10) and electrically connected between the housing (10) and the distal end of the third through-hole connection (3).

Description

[0001] The inventive concepts relate generally to through-hole DFB lasers (DFB = distributed feedback) and, more particularly, to techniques for improving the bandwidth of through-hole DFB lasers.

[0002] DFB lasers typically comprise a light-emitting laser diode (LD) and a monitoring photodiode (PD). These components may be mounted in a through-hole package, which has leads (or terminals, or pins) extending through one side of a circuit board and soldered to pads on the other side of the board. The leads are typically relatively long, and as a result, bandwidth loss can occur, primarily due to parasitic inductances. For example, if an input of the DFB laser is coupled to an oscilloscope probe used in testing or analyzing a device under test, an inductance can cause the laser diode (LD) current to drop, thereby limiting the measurement bandwidth.

[0003] To date, the approach to increasing the bandwidth of a through-hole laser (or other electronic components) has been to mount the laser in such a way that the length of the through-hole lines is limited to a practical level. This can improve bandwidth to a certain extent, but further improvements in bandwidth remain desirable.

[0004] The object of the present invention is to provide a laser emitting device, a probe arrangement and methods for improving the bandwidth of a through-hole laser emitting device with improved characteristics.

[0005] This object is achieved by a device according to claim 1, an arrangement according to claim 9 and methods according to claims 12 and 15.

[0006] According to one aspect of the inventive concepts, a laser-emitting device is provided, comprising a housing and first, second, and third through-hole leads protruding through the housing. A proximal end portion of each of the first to third through-hole leads is located within the housing, and a distal end portion of each of the first to third through-hole leads is located outside the housing. The laser-emitting device further comprises a laser diode and a photodiode located within the housing.The laser diode includes a cathode electrically connected to the proximal end portion of the first through-hole lead wire and an anode electrically connected to the proximal end portion of the second through-hole lead wire. The photodiode includes a cathode electrically connected to the anode of the laser diode and an anode electrically connected to the proximal end portion of the third through-hole lead wire. The laser-emitting device further includes a resistor attached to an exterior of the housing and electrically connected between the housing and the distal end of the third through-hole lead wire.

[0007] The laser diode may be a distributed feedback laser diode.

[0008] A length of the third through-hole lead outside the package may be shorter than a length of each of the first and second through-hole lead outside the package.

[0009] The distal end portion of the third through-hole lead may terminate at the connection with the resistor.

[0010] Respective resistor leads may be soldered to the distal end of the third through-hole lead and the package.

[0011] The anode of the photodiode may be wire-connected to the proximal end portion of the third through-hole lead, the cathode of the photodiode may be wire-connected to the anode of the laser diode, the cathode of the laser diode may be wire-connected to the proximal end portion of the first through-hole lead, and the anode of the laser diode may be wire-connected to the proximal end portion of the second through-hole lead.

[0012] The laser-emitting device may further include a fourth through-hole lead that protrudes through the housing and is electrically connected to the housing. The fourth through-hole lead may be a ground lead.

[0013] According to another aspect of the inventive concepts, a probe assembly is provided that includes the laser emitting device described above, a direct current (DC) bias voltage source electrically connected to the distal end of the second through-hole lead, and a probe assembly electrically connected to the distal end of the first through-hole lead.

[0014] The probe assembly may include a probe tip, an amplifier having an input electrically connected to an output of the probe tip, and a resistor electrically connected between an output of the amplifier and the distal end portion of the first through-hole lead. The housing may be grounded.

[0015] According to another aspect of the inventive concepts, a method for improving the bandwidth of a through-hole laser emitting device is provided. The through-hole laser emitting device includes a laser diode and a monitor photodiode in a package and a plurality of through-hole leads extending through the package. The method includes severing, outside of the package, one of the through-hole leads connected to an anode of the monitor photodiode, wherein a severed end of the one of the through-hole leads is in close proximity to an exterior surface of the package, and attaching a resistor to an exterior of the package such that the resistor is electrically connected between the package and the severed end of the one of the through-hole leads.

[0016] The laser diode may be a distributed feedback (DFB) laser diode. The method may further include reverse-biasing the monitoring photodiode during operation of the DFB laser.

[0017] Preferred embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. They show: Fig. 1 an exemplary perspective view from above and from the side of a DFB laser and Fig. Figure 1B is a perspective view of the bottom of the DFB laser; Fig. Figure 2A is an exemplary schematic cross-sectional view of the DFB laser of Fig. 1A; Fig. Figure 2B is an example equivalent circuit diagram of the DFB laser of Fig. 1A; Fig. 3 is an exemplary schematic cross-sectional view of a DFB laser according to an embodiment of the inventive concepts; Fig. 4 illustrates an equivalent circuit diagram of a through-hole DFB laser connected to a probe assembly according to an embodiment of the inventive concepts; Fig. 5 is a simplified circuit diagram of the probe arrangement of Fig. 4, which is operatively connected to an oscilloscope; Fig. 6 and Fig. 7 are flowcharts for reference in describing alternative methods for achieving RLC switching of embodiments of the inventive concepts; Fig. 8 is a diagram for reference in describing the effects of the above-described embodiment; Fig. 9A illustrates an example of the frequency response without an RLC network of the present embodiments; and Fig. 9B illustrates an example of the frequency response with the RLC network of the present embodiments.

[0018] In the following detailed description, for purposes of illustration and not limitation, illustrative embodiments are described, disclosing specific details in order to provide a thorough understanding of an embodiment in accordance with the present teachings. Descriptions of well-known systems, devices, materials, methods of operation, and methods of manufacture may be omitted to avoid obscuring the description of the illustrative embodiments. Nevertheless, systems, devices, materials, and methods that are within the skill of one of ordinary skill in the art are within the scope of the present teachings and may be used in accordance with illustrative embodiments. It is understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.The defined terms are in addition to the technical and scientific meanings of the defined terms as commonly understood and recognized in the technical field of the present teachings.

[0019] Although the terms first, second, third, etc. may be used herein to describe various elements or components, it is understood that these elements or components should not be limited by these terms. The terms are used merely to distinguish one element or component from another element or component. Thus, a first element or component discussed below could be referred to as a second element or component without departing from the teachings of the present disclosure.

[0020] As used herein in the specification and the appended claims, the singular forms of the terms "a," "an," and "the" are intended to include both singular and plural forms unless the context clearly indicates otherwise. Furthermore, the terms "comprises" and / or "comprising" and / or similar terms used in this specification specify the presence of the listed features, elements, and / or components, but do not preclude the presence or addition of one or more other features, elements, components, or groups thereof. As used herein, the term "and / or" includes any and all components of one or more of the associated listed elements.

[0021] With regard to the drawings, it is emphasized that the features and elements depicted are not necessarily to scale. Indeed, dimensions may be enlarged or reduced as desired to clarify the explanation. Where applicable and practical, like reference numerals refer to like elements.

[0022] The present disclosure is thus intended, through one or more of its various aspects, embodiments, and / or specific features, to provide one or more of the advantages specifically listed below.

[0023] Fig. 1A is an exemplary top and side perspective view of a DFB laser 101 and Fig. Figure 1B is a perspective view of the bottom of the DFB laser 101.

[0024] With reference to Fig. 1A and Fig. 1B, the DFB laser 101 of this example includes a housing 10 having a base 11 and a cover 12 fixed to the top of the base 11. Both the base 11 and the cover 12 can be made of the same or different metals or metal alloys, such as copper or a copper alloy. As explained below, the housing 10 contains a photodiode and a laser diode. The laser diode is positioned within the housing 10 to emit a laser beam through a window 13 located in the top surface of the cover 12, or alternatively, into a connected fiber. The photodiode is also positioned within the housing 10 and detects (monitors) an output power of the laser diode.

[0025] Also in the example of Fig. 1A and Fig. 1B, the DFB laser 101 includes a plurality of through-hole leads 14 projecting from through-holes 15 located in the base 11. For this reason, the DFB laser 101 may also be referred to as a "through-hole DFB laser." The illustrated example includes four (4) through-hole leads 14. However, depending on the internal circuitry of the DFB laser 101, more than four or fewer than four through-hole leads may be provided.

[0026] Fig. Figure 2A is an exemplary schematic cross-sectional view of the DFB laser 101. As shown, the cover 12 is fixed to an upper surface of the base 11, and through-hole lead wires 14a and 14b protrude from the lower surface of the base 11. Light emitted from the laser 101 can either exit to the outside through a window (e.g., window 13) in the top of the through-hole housing or into a connected optical fiber for transport to a receiving optical-electrical module in the system. For convenience of the drawing, Fig. 2A only two (2) through-hole connecting leads 14a and 14b, but it is clear that additional through-hole connecting leads may be provided. Fig. 2A also shows the through-hole lead 14b extending through a through-hole 15 in the base 11. In the illustrated example, the through-hole lead 14b is insulated from the base 11 by an insulating material 18. The insulating material 18 may be made of glass, for example. All remaining through-hole leads of the DFB laser 101 may be similarly configured, except for one through-hole lead (if any) that serves to electrically ground the package 10. Each such grounded through-hole lead may be electrically connected directly or indirectly to the base 11.

[0027] With further reference to Fig. 2A, the base 11 includes support surfaces in the housing 10 for supporting a photodiode 20 and laser diode 21. In particular, the laser diode 21 may be attached to a heat sink 16 that is fixed to the base 11 in the housing 10. In this particular example, the laser diode 21 is configured to emit laser light 22 from a light-emitting surface thereof and a monitor light 23 from an opposite surface thereof. The monitor light 23 is incident on the photodiode 20, which detects an output power of the laser diode 21. Furthermore, in this example, the laser diode 21, photodiode 20, and through-hole lead wires 14a and 14b are connected by connecting wires 17 to form a circuit as shown in Fig. 2B, which is described below.

[0028] Fig. 2B is an exemplary equivalent circuit diagram of the DFB laser 101. In the figure, representative through-hole leads of the DFB laser 101 are denoted by the numbers 1, 2, 3, and 4 in boxes. As shown, a cathode of the laser diode LD is electrically connected to the first through-hole lead, and an anode of the laser diode LD is electrically connected to a second through-hole lead 2. Further, a cathode of the photodiode PD is electrically connected to the second through-hole lead 2 (i.e., to the anode of the laser diode LD), and an anode of the photodiode PD is electrically connected to a third through-hole lead 3. In addition, the package 10 may be electrically connected to a fourth through-hole lead 4.

[0029] During operation, a DC bias voltage may be applied to the second through-hole lead 2, while an input signal (e.g., a radio frequency (RF) signal from a test probe) may be applied to the first through-hole lead 1. An output power of the laser diode LD depends on the current flowing through the laser diode and a temperature of the laser diode. Meanwhile, the photodiode PD receives a portion of the total light emitted by the laser diode LD and outputs a voltage correlated with the output power of the laser diode LD. In some examples, light emitted by the laser diode LD is input to the optical input of an oscilloscope or similar analyzing device.

[0030] As explained above, the interior of the through-hole package of a laser diode may include a photodiode that can be used to monitor the diode output. However, in some applications, the photodiode is not needed and is therefore not used for its intended purpose (i.e., monitoring). As explained below, in embodiments of the inventive concepts, the unused photodiode can be used to implement a series RLC network, which can improve the bandwidth of the laser diode—i.e., cause the current in the laser diode to decrease in frequency. The inductance L of this network is the parasitic inductance of through-hole leads (pins) and wire bonds. The capacitance C is the capacitance of the blocked (i.e., turned off) photodiode.The resistance R is an external resistor (surface-mounted or otherwise) connected to a through-hole lead from the photodiode to the laser housing ground. Inductance applied to this external resistor can be used to tune the response.

[0031] Fig. Figure 3 is an exemplary schematic cross-sectional view of a DFB laser 201 according to an embodiment of the inventive concepts. In the example of this embodiment, a DFB laser 201 is a version of the DFB laser 101 described above in connection with Fig. 1A to 2B, which is modified after manufacture. Therefore, like elements in the figures are designated by the same reference numerals.

[0032] With reference to Fig. 3, a housing 10 includes a base 11 and a cover 12 fixed to the top of the base 11. Both the base 11 and the cover 12 can be made of the same or different metals or metal alloys, such as copper or a copper alloy. The housing 10 contains a photodiode 20 and a laser diode 21. The laser diode 21 is positioned within the housing 10 to emit a laser beam through a window 13 located in the top surface of the cover 12. In embodiments of the inventive concepts, the laser diode 21 is a DFB laser diode.

[0033] The cover 12 is fixed to an upper surface of a base 11 and pins 25 and 14b protrude from the lower surface of the base 11. For the simplification of the drawing, Fig. 3 only two (2) pins 25 and 14b, but it is clear that additional pins may be provided. Fig. Figure 3 also shows pin 14b extending through a through-hole 15 in base 11. In the illustrated example, pin 14b is insulated from base 11 by an insulating material 18. The insulating material 18 may be made of glass, for example. All remaining pins of DFB laser 101 may be similarly configured, except for one pin (if any) that serves to electrically ground package 10. Each grounded pin may be electrically connected directly or indirectly to base 11.

[0034] With further reference to Fig. 3, the base 11 includes support surfaces in the housing 10 for supporting a photodiode 20 and laser diode 21. In particular, the laser diode 21 may be attached to a heat sink 16 that is fixed to the base 11 in the housing 10. In this particular example, the laser diode 21 is configured to emit laser light 22 from a light-emitting surface thereof and a monitor light 23 from an opposite surface thereof. The monitor light 23 may be incident on the photodiode 20. Also in this example, the laser diode 21, photodiode 20, and through-hole leads 14a and 14b are connected by connecting wires 17 to form a circuit as shown in Fig. 4, which will be described below. It should be noted that in this example, the through-hole lead 25 is connected to the anode of the photodiode 21.

[0035] The DFB laser 201 further includes a resistor 30 outside the package 10. In this example, the resistor 30 is attached to the bottom surface of the base 11 by solder 31 and 32. Specifically, the solder 31 connects one terminal of the resistor 30 to the through-hole lead 25 and another terminal of the resistor 30 to the base 11. However, the inventive concepts are not limited to the manner in which the resistor 30 is attached to the package 10, as long as the end result is that the resistor 30 is electrically connected between the through-hole lead 25 (which is connected to the anode of the photodiode 20) and a reference voltage, such as ground.

[0036] As it is in Fig. 3, the through-hole lead 25 is severed in close proximity to the base 11. Therefore, a length of the through-hole lead 25 outside the package is less than a length of all the remaining through-hole lead outside the package.

[0037] In some embodiments of the inventive concepts, an input of the through-hole DFB laser is connected to the output of a probe assembly, such as the probe assembly of an oscilloscope or other test equipment. Fig. 4 illustrates an equivalent circuit diagram of a through-hole DFB laser 401 connected to a probe assembly 501 according to an embodiment of the inventive concepts.

[0038] With reference to Fig. 4, a photodiode PD and a laser diode LD are contained in a package 10. In the figure, reference numerals 1, 2, 3, and 25 denote through-hole leads of the through-hole DFB laser 401, and L1 to L6 denote parasitic inductances of the through-hole leads and all connecting wires connected between the through-hole leads and the photodiode PD and the laser diode LD.

[0039] The through-hole lead 25 connected to the anode of the photodiode PD would normally include a parasitic inductance L8. However, as represented by the X across L8, this inductive component is removed by severing the through-hole lead 25 in close proximity to the outer surface of the package 10, as described above. As also described above, a resistor R1 is connected between the severed lead 25 and the package 10. The resistor R1 of Fig. 4 corresponds to the resistance 30 of Fig. 3.

[0040] A direct current (DC) bias voltage source is electrically connected to the distal end of the second through-hole lead 2. In the example of Fig. 4, the DC bias source comprises a voltage source V and a filter capacitor C. Here, the laser diode LD is forward biased and, as described above, the photodiode PD is reverse biased.

[0041] The probe array 501 is connected to the input of the through-hole DFB layer 401. That is, as shown in Fig. 4, the probe assembly 501 is connected to the distal end of the through-hole lead 1, which is coupled to the anode of the laser diode LD. In the example of Fig. 4, the probe assembly includes a probe tip 502, an amplifier 503 having an input electrically connected to an output of the probe tip, and a resistor 504 electrically connected between an output of the amplifier 503 and the distal end portion of the first through-hole lead 1. However, the inventive concepts are not limited by the specifics of the probe assembly 501. In operation, the electrical signals received by the probe tip 502 are amplified and applied to the cathode of the laser diode LD, and the laser light emitted by the laser diode LD is modulated according to the thus applied electrical signals.

[0042] Furthermore, in the example of the present embodiment, the housing 10 is grounded, whereby the resistor R1 is also grounded.

[0043] Fig. 5 is a simplified circuit diagram of the probe assembly 501 of Fig. 4, which is operatively connected to an oscilloscope 900. Like reference numerals refer to like elements and a description of the elements already used in connection with Fig. 4 will not be repeated below to avoid redundancy in the description.

[0044] As it is in Fig. As shown in Figure 5, the laser light emitted by the laser diode LD is applied to one end of an optical carrier (e.g., optical cable) 600. The laser light propagates through the carrier 600 and strikes a photodiode 700, which converts the laser light energy into an electrical signal. The electrical signal output by the photodiode 700 is amplified by an amplifier 800 and applied to the oscilloscope 900, where it is displayed and / or analyzed.

[0045] As described above, in at least some embodiments of the inventive concepts, the through-hole lead coupled to the photodiode of the DFB laser is cut to substantially eliminate its parasitic inductance, and a resistive element is coupled between the lead and package (or ground) to add a resistive component that improves the bandwidth of the DFB laser when the photodiode is reverse biased. Fig. 6 and Fig. 7 are flow diagrams for reference in describing alternative methods for achieving this modification.

[0046] With reference to Fig. 6, at S601, one of the through-hole leads connected to an anode of the monitoring photodiode is severed outside the package, where a severed end of the one of the through-hole leads is preferably in close proximity to an outer surface of the package.

[0047] Next, a resistor, known as S602, is attached to an outer surface of the package, so that the resistor is electrically connected between the package and the severed end of one of the through-hole leads. Here, the resistor can be attached using solder or other suitable means.

[0048] Alternatively, with reference to Fig. 7, at S701, a resistor is attached to an outer side of the package, such that the resistor is electrically connected between the package and one of the through-hole leads, which is connected to an anode of the monitoring photodiode. Again, the resistor can be attached by solder or other suitable means.

[0049] Next, as S702, one of the through-hole lead wires connected to the anode of the monitor photodiode is severed outside the package, wherein a severed end of the one of the through-hole lead wires is preferably in close proximity to an outer surface of the package.

[0050] As used above, “closest proximity” means that the severed end of the through-hole lead is as close as practically possible to the package, but still projects from the package by an amount sufficient to practically permit soldering of the resistor to the through-hole lead (see Fig. 6). Or in the case where the resistor is soldered to the package before the through-hole lead is cut (as in Fig. 7), the through-hole lead is severed as close to the solder as practically possible without damaging the solder.

[0051] Fig. Figure 8 is a diagram for reference in describing the effects of the above-described embodiment. As described above, in embodiments of the inventive concepts, the unused photodiode can be used to implement a series RLC network, which can improve the bandwidth of the laser diode—that is, cause the current in the laser diode to decrease its drop with frequency. The inductance L of this network is the parasitic inductance of through-hole leads (pins) and wire bonds. The capacitance C is the capacitance of the blocked (i.e., turned off) photodiode. The resistance R is an external resistor (surface-mounted or otherwise) connected to a through-hole lead from the photodiode to the chassis ground of the laser package. Inductance introduced into this external resistor can be used to tune the response.

[0052] With reference to Fig. 8, a first series L-shunt C network is present at the input of the laser diode LD. The impedance entering a second series L-shunt C network 802 will increase with frequency. The second series L-shunt C network 802 bypasses it and appears inductive across the bandwidth of interest. Without the series RLC network 803, this can cause the current in the laser diode LD to decrease with frequency, thus reducing the light output of the laser diode LD versus frequency. With the proper compensating input impedance of the series RLC network, the current in the laser diode LD can be maintained, thereby expanding the bandwidth of the output light. For a particular through-hole laser diode, the placement and value of the resistor terminating the series RLC network can be determined empirically.

[0053] Next, the graphs of Fig. 9A and Fig. 9B is referred to.

[0054] Fig. Figure 9A shows an example of the impedance of the photodiode LD to ground relative to the frequency. As shown, the impedance drops mainly according to a capacitance C of the photodiode LD to a minimum Z, where Z is determined by the resistance R of the resistor 30 ( Fig. 3) is set as described above in connection with Fig. 8. Above the resonant frequency, the impedance then gradually increases, as shown.

[0055] Fig. 9B illustrates an example of the frequency response (in dB) of an unmodified DFB laser diode package (the dashed line) and a DFB laser diode package modified according to the embodiments described herein (the solid line). As shown, peaking is reduced in the compensated response relative to the uncompensated response.

[0056] Furthermore, the inductance is after the minimum Z ( Fig. 9A) at the impedance in parallel with the inductance of the second series L-shunt C network described above in connection with Fig. 8. This reduces the net impedance L and the frequency at which the current in the laser begins to decrease is shifted upwards, increasing the obtained bandwidth.

[0057] The illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The illustrations are not intended to serve as a complete description of all elements and features of the disclosure described herein. Many other embodiments will be apparent to those skilled in the art upon review of the disclosure. Other embodiments may be utilized and derived from the disclosure, so that structural and logical substitutions and changes may be made without departing from the scope of the disclosure. Additionally, the illustrations are merely representative and may not be to scale. Certain proportions within the illustrations may be exaggerated, while other proportions may be minimized.Accordingly, the disclosure and the figures are to be considered as illustrative, and not as restrictive.

[0058] One or more embodiments of the disclosure may be referred to herein, individually and / or collectively, by the term "invention" merely for convenience and without knowingly intending to limit the scope of this application to any particular invention or inventive concept. Furthermore, it should be recognized that although specific embodiments have been illustrated and described herein, any subsequent arrangement designed to achieve the same or similar purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all subsequent adaptations or variations of various embodiments. Combinations of the above embodiments, as well as other embodiments not specifically described herein, will be apparent to those skilled in the art upon review of the specification.

[0059] The Summary of Disclosure complies with 37 CFR §1.72(b) and is presented with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Additionally, in the foregoing Detailed Description, for the purpose of streamlining the disclosure, various features may be grouped together or described in a single embodiment. This disclosure should not be construed as reflecting an intent that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, the inventive subject matter may be directed to fewer than all of the features of any one of the disclosed embodiments.Thus, the following claims are incorporated into the detailed description, with each claim standing as defining separately claimed subject matter.

[0060] The foregoing description of the disclosed embodiments is provided to enable any person skilled in the art to practice the concepts described in the present disclosure. Thus, the above-disclosed subject matter should be considered as illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, improvements, and other embodiments that fall within the true spirit and scope of the present disclosure. Thus, the scope of the present disclosure is to be determined, to the maximum extent permitted by law, by the broadest permissible interpretation of the following claims and their equivalents, and is not to be restricted or limited by the foregoing detailed description.

Claims

[1] Laser (101) emitting device having the following features: a housing (10); first, second and third through-hole connecting lines (14) projecting through the housing (10), wherein a proximal end portion of each of the first to third through-hole connecting lines (14) is located inside the housing (10) and a distal end portion of each of the first to third through-hole connecting lines (14) is located outside the housing (10); a laser diode (21) located in the housing (10), the laser diode (21) comprising a cathode electrically connected to the proximal end portion of the first through-hole lead (1) and an anode electrically connected to the proximal end portion of the second through-hole lead (2); a photodiode (20) located in the housing (10), the photodiode (20) comprising a cathode electrically connected to the anode of the laser diode (21) and an anode electrically connected to the proximal end portion of the third through-hole lead (3); and a resistor (30) attached to an outer side of the housing (10) and electrically connected between the housing (10) and the distal end of the third through-hole lead (3). [2] A laser (101) emitting device according to claim 1, wherein the laser diode (21) is a distributed feedback laser diode (21). [3] The laser (101) emitting device according to claim 1 or 2, wherein a length of the third through-hole lead (3) outside the package (10) is shorter than a length of each of the first and second through-hole lead (14) outside the package (10). [4] A laser (101) emitting device according to any one of claims 1 to 3, wherein the distal end portion of the third through-hole lead (3) terminates at the connection with the resistor (30). [5] A laser (101) emitting device according to claim 4, wherein respective lead wires of the resistor (30) are soldered to the distal end of the third through-hole lead wire (3) and to the housing (10). [6] The laser (101) emitting device according to any one of claims 1 to 5, wherein the anode of the photodiode (20) is wire-connected to the proximal end portion of the third through-hole lead (3), the cathode of the photodiode (20) is wire-connected to the anode of the laser diode (21), the cathode of the laser diode (21) is wire-connected to the proximal end portion of the first through-hole lead (1), and the anode of the laser diode is wire-connected to the proximal end portion of the second through-hole lead (2). [7] The laser (101) emitting device according to any one of claims 1 to 6, further comprising a fourth through-hole lead (4) projecting through the housing (10) and electrically connected to the housing (10). [8] DFB laser (101) according to claim 7, wherein the fourth through-hole lead (4) is a ground lead (25). [9] Probe assembly (501) having the following features: the laser (101) emitting device according to claim 1; a direct current (DC) bias voltage source electrically connected to the distal end of the second through-hole lead (2); a probe assembly (501) electrically connected to the distal end of the first through-hole lead (1). [10] Probe assembly (501) according to claim 9, wherein the probe assembly (501) has the following features: a probe tip (502); an amplifier (503) having an input electrically connected to an output of the probe tip (502); and a resistor (30) electrically connected between an output of the amplifier (503) and the distal end portion of the first through-hole lead (1). [11] Probe assembly (501) according to claim 10, wherein the housing (10) is grounded. [12] A method for improving the bandwidth of a through-hole (15) laser (101) emitting device, the through-hole (15) laser (101) emitting device comprising a laser diode (21) and a monitoring photodiode (20) in a housing (10), and a plurality of through-hole lead wires (14) extending through the housing (10), the method comprising the steps of: Cutting, outside the housing (10), one of the through-hole leads (14) connected to an anode of the monitoring photodiode (20), wherein a cut end of the one of the through-hole leads (14) is in close proximity to an outer surface of the housing (10); and Attaching a resistor (30) to an outer side of the housing (10) such that the resistor (30) is electrically connected between the housing (10) and the severed end of one of the through-hole lead wires (14). [13] A method according to claim 12, wherein the laser diode (21) is a diode (21) of a distributed feedback laser. [14] The method of claim 13, further comprising reverse biasing the monitor photodiode (700) during operation of the DFB laser (101). [15] A method for improving the bandwidth of a through-hole (15) laser (101) emitting device, the through-hole (15) laser (101) emitting device comprising a laser diode (21) and a monitoring photodiode (20) in a housing (10), and a plurality of through-hole connecting lines (14) extending through the housing (10), the method comprising the steps of: Attaching a resistor (30) to an outer side of the housing (10) such that the resistor (30) is electrically connected between the housing (10) and one of the through-hole lead wires (14) connected to an anode of the monitoring photodiode (20); and Cutting, outside the housing (10), one of the through-hole lead wires (14) connected to the anode of the monitoring photodiode (20), wherein a cut end of the one of the through-hole lead wires (14) is in close proximity to an outer surface of the housing (10). [16] A method according to claim 15, wherein the laser diode (21) is a diode (21) of a distributed feedback laser. [17] The method of claim 16, further comprising reverse biasing the monitor photodiode (700) during operation of the DFB laser (101).

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