Laser arrangement and method for producing a laser arrangement

Abstract

It is provided a laser arrangement, having an electro-absorption-modulated laser, having a laser section and an electro-absorption modulator section; a current source for supplying the laser section with current; a DC voltage source that is arranged in addition to the current source and can be used to apply DC voltage to a diode structure of the electro-absorption modulator section; a driver with which an RF signal is able to be fed to the laser; and an electrical connection via which the driver is connected to the laser. The electrical connection provides a direct current connection between the driver and the laser such, and the driver is configured such, that a photocurrent that is generated in the electrode-absorption modulator section of the laser by illumination with light of the laser section at least partially flows to the driver and at least contributes to the energy supply of the driver.

Claims

1. A laser arrangement, having: an electro-absorption-modulated laser, having a laser section and an electro-absorption modulator section; a current source for supplying the laser section with current; a DC voltage source that is arranged in addition to the current source and can be used to apply DC voltage to a diode structure of the electro-absorption modulator section; a driver with which an RF signal is able to be fed to the laser; an electrical connection via which the driver is connected to the laser, wherein the electrical connection provides a direct current connection between the driver and the laser and the driver is configured such that a photocurrent that is generated in the electrode-absorption modulator section of the laser by illumination with light of the laser section at least partially flows to the driver and at least contributes to the energy supply of the driver.

2. The laser arrangement as claimed in claim 1, wherein the electrical connection also provides an RF connection between the driver and the laser.

3. The laser arrangement as claimed in claim 2, wherein the electrical connection is an impedance-adapted line.

4. The laser arrangement as claimed in claim 1, wherein the driver is a single-ended amplifier.

5. The laser arrangement as claimed in claim 4, wherein the RF signal is able to be supplied to the driver by virtue of a temporally varying potential being applied to an input of the driver, wherein the RF signal is produced as difference of the varying potential with a temporally substantially constant reference potential.

6. The laser arrangement as claimed in claim 1, wherein the driver is configured such, and connected to the laser such, that at least one of: the driver is able to be supplied with energy exclusively by way of the photocurrent generated in the electro-absorption modulator section of the laser, and the driver retains its amplification properties if it is supplied with energy exclusively by way of the photocurrent generated in the electro-absorption modulator section of the laser.

7. The laser arrangement as claimed in claim 1, wherein a current generated by the current source at least substantially does not flow into the driver.

8. The laser arrangement as claimed in claim 1, wherein no electrical connection exists between the current source and the electro-absorption modulator section or that an electrical connection which does not carry current during the operation of the laser arrangement is formed, in particular exclusively via at least one doped semiconductor layer of the laser.

9. The laser arrangement as claimed in claim 1, wherein no electrical connection exists between the current source and the driver or an electrical connection which does not carry current during the operation of the laser arrangement is formed, in particular exclusively via at least one doped semiconductor layer of the laser.

10. The laser arrangement as claimed in claim 1, wherein no electrical connection exists between the DC voltage source and the laser section or an electrical connection is formed exclusively via at least one doped semiconductor layer of the laser.

11. The laser arrangement as claimed in claim 1, wherein the energy supply of the driver is effected at least one of: mainly by way of the photocurrent produced in the electro-absorption modulator section of the laser, and at least substantially solely by way of the photocurrent produced in the electro-absorption modulator section of the laser.

12. The laser arrangement as claimed in claim 1, wherein the laser arrangement is configured such that at least substantially the entire photocurrent generated in the electro-absorption modulator section is used for the energy supply of the driver.

13. The laser arrangement as claimed in claim 1, wherein the driver is a traveling wave amplifier.

14. The laser arrangement as claimed in claim 1, further comprising an impedance adaptation circuit having an adaptation inductance, an adaptation resistance and/or a direct current blocking capacitance.

15. The laser arrangement as claimed in claim 14, wherein at least one of: the impedance adaptation circuit does not have a direct current blocking capacitance, the impedance adaptation circuit is part of the laser and the impedance adaptation circuit is integrated in the electrical connection.

16. The laser arrangement as claimed in claim 1, wherein the driver, the electrical connection and the laser are monolithically integrated.

17. The laser arrangement as claimed in claim 1, wherein the electrical connection is formed by a flexible line.

18. The laser arrangement as claimed in claim 1, further comprising a thermoelectric cooling apparatus for cooling the electro-absorption modulated laser.

19. An array having a plurality of laser arrangements as claimed in claim 1.

20. A method for producing a laser arrangement having the steps: providing an electro-absorption-modulated laser, having a laser section and an electro-absorption modulator section; providing a current source for supplying the laser section with current and an additional DC voltage source that is arranged in addition to the current source and can be used to apply DC voltage to a diode structure of the electro-absorption modulator section; providing a driver with which an RF signal is able to be fed to the laser; producing an electrical connection between the driver and the laser, wherein the laser arrangement is configured such that the electrical connection provides a direct current connection between the driver and the laser such that a photocurrent that is generated in the electrode-absorption modulator section of the laser by illumination with light of the laser section at least partially flows to the driver and at least contributes to the energy supply of the driver.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The proposed solution will be explained in more detail below on the basis of embodiments with reference to the figures.

(2) FIG. 1 schematically shows a laser arrangement according to a first embodiment.

(3) FIG. 2 shows a perspective view of a laser arrangement according to a second embodiment.

(4) FIG. 3 shows a circuit diagram of a laser arrangement according to a third embodiment.

(5) FIG. 4 shows a variant of the laser arrangement from FIG. 3.

(6) FIG. 5 shows a further variant of the laser arrangement from FIG. 3.

(7) FIG. 6 shows a circuit diagram of a laser arrangement according to a fourth embodiment.

(8) FIG. 7 shows a variant of the laser arrangement from FIG. 6.

(9) FIG. 8 shows a circuit diagram of a laser arrangement according to a fifth embodiment.

(10) FIG. 9 shows a circuit diagram of a laser arrangement according to a sixth embodiment.

(11) FIG. 10 shows a circuit diagram of a laser arrangement according to a seventh embodiment.

DETAILED DESCRIPTION

(12) The laser arrangement 1 according to the proposed solution, illustrated in FIG. 1, comprises an electro-absorption-modulated laser (EML) 11, having a laser section 111 (for example in the form of a DFB or DBR laser) and an electro-absorption modulator section 112. A (for example thermoelectric) cooling apparatus 12 on which the laser 11 is arranged can be provided for cooling said laser 11. According apparatus 12, however, is merely optional.

(13) For actuating the laser 11, in particular for transmitting an RF signal, the laser arrangement 1 comprises a driver 13, in particular in the form of a traveling wave amplifier (TWA). The driver 13 in particular serves for amplifying a radio-frequency input signal V.sub.RFin and for feeding the amplified RF signal to the laser 11 via an electrical connection 14.

(14) The electrical connection 14 not only realizes an RF connection between the driver 13 and the laser 11, but at the same time provides a direct current connection between the driver 13 and the laser 11. Moreover, the laser arrangement 1 is configured such that a photocurrent I.sub.photo generated in the electro-absorption modulator section 112 of the laser 11 upon irradiation with light of the laser section 111 at least partially flows into the driver 13 via the electrical connection 14 and at least contributes to the energy supply of the driver 13.

(15) It is in particular conceivable that the energy supply of the driver 13 is effected exclusively by way of the photocurrent I.sub.photo. However, it is also possible that an additional supply voltage V.sub.TWA is supplied to the driver 13 via a voltage source. In particular, the driver 13 is configured such that it makes possible both energy supply exclusively by way of the photocurrent I.sub.photo and with the additional supply voltage V.sub.TWA.

(16) A possible hybrid configuration of the laser arrangement 1 according to the solution is illustrated in FIG. 2. Here, the driver 13 is arranged as an integrated circuit on a first substrate 130, while the EML 11 is formed as a semiconductor structure on a separate, second substrate 110.

(17) The driver 13 and the EML 11 are coupled to one another via a likewise separate electrical connection 14, wherein the electrical connection 14 has the form of a flexible line, that is to say a line comprising a plurality of conductor tracks 142 which are arranged on a flexible substrate 141. The conductor tracks 142 are connected via contacts (bumps) 143 to output lines of the driver 13 or input lines of the laser 11.

(18) The driver 13 is additionally coupled to a broadband termination coil (decoupling coil) 131, via which a supply voltage is able to be supplied to the driver 13. The supply voltage is made available in addition to the supply by way of the photocurrent of the laser 11 supplied via the electrical connection 14. Such an additional voltage supply and consequently also the termination coil 131, however, are merely optional.

(19) FIG. 3 shows a circuit diagram of a further embodiment of the laser arrangement 1 according to the solution. Accordingly, the laser arrangement 1 additionally has a DC voltage source 15, via which DC voltage (reverse voltage V.sub.rev) can be applied to a diode structure 1121 of the electro-absorption modulator section 112 of the laser 11. In addition, a current source 17 for supplying the laser section 111 with current (supply current I.sub.DFB) is provided.

(20) However, a separate voltage supply of the driver 13 was dispensed with, that is to say the energy for operating the driver 13 is made available solely by the DC current I*.sub.photo that is supplied via the electrical connection 14 from the laser 11, such that the only energy sources required for operating the laser arrangement 1 are the DC voltage source 15 and the current source 17.

(21) The continuous light radiation (P.sub.optCW) generated by the laser section 111 is modulated using the diode structure 1121 and in dependence on the RF voltage supplied to the laser 11 via the driver 13, wherein the EML emits modulated radiation (P.sub.optmod) and the photocurrent I.sub.photo is produced in the electro-absorption modulator section 112. The photocurrent I.sub.photo is supplied to the driver 13, as already explained above, via the electrical connection 14, specifically in particular the amplification transistors 133 (TWA) thereof.

(22) The laser arrangement 1 furthermore comprises an impedance adaptation circuit 16 for adapting in particular the impedance of the electro-absorption modulator section 112 of the laser 11 to the impedance of the connection 14 and of the driver 13 to keep reflections of the driver signal as low as possible. The impedance adaptation circuit 16 in the embodiment of FIG. 3 is correspondingly configured as a termination impedance circuit of the laser 11 and comprises an adaptation inductance 161 (L.sub.term), an adaptation resistance 162 (termination resistance R.sub.term) and a direct current blocking capacitance 163 (C.sub.block). The adaptation inductance 161, the adaptation resistance 162 and the direct current blocking capacitance 163 are connected in series.

(23) The direct current blocking capacitance 163 in particular prevents draining of a part of the photocurrent I.sub.photo and of a current I.sub.RTERM originating from the voltage source 15 via the termination resistance R.sub.term. Accordingly, the driver 13 is fed at least substantially by way of the direct current I*.sub.photo flowing from the laser 11 to the driver 13, wherein here the direct current I*.sub.photo flowing to the driver 13 corresponds to the photocurrent I.sub.photo generated (that is to say, I*.sub.photo=I.sub.photo).

(24) Also conceivable is that the direct current blocking capacitance 163 is dispensed with and replaced by a short circuit, as a result of which production of the impedance adaptation circuit can be simplified. This variant is illustrated in FIG. 4. In this case, the direct current I.sub.RTERM together with the photocurrent I.sub.photo generated in the electrode-absorption modulator section 112 will flow to the driver 13 such that, for the current I*.sub.photo supplied to the driver 13: I*.sub.photo=I.sub.photo+I.sub.RTERM.

(25) It is also conceivable that the termination resistance R.sub.term replaces the output resistance (pull-up resistance) R.sub.L of the driver 13 (in particular in a monolithic configuration of the laser arrangement 1) and the driver 13 is supplied in supplementation of the photocurrent from the electro-absorption modulator section 112 via the termination resistance R.sub.term (=R.sub.L). The driver-side resistance R.sub.L on the transistor Q is dispensed with (open-collector driver configuration), as is shown in FIG. 5. As a result, in particular the construction of the base potential divider (comprising the resistances RB2 and Rb) which is supplied with a low current of the voltage source 15 (V.sub.rev) is simplified; in particular by virtue of the fact that the inductance Lb which is series-connected with the resistance Rb is now immediately grounded. Via a capacitance C.sub.input and a resistance R.sub.g and the base potential divider, a modulated radio-frequency input current I.sub.PRBS is supplied to the transistors 133.

(26) FIG. 6 shows a circuit diagram of a laser arrangement 1 according to the solution, which is configured similar to the embodiment of FIG. 3, but wherein further details of the driver 13, in the form of a traveling wave amplifier, are illustrated. Likewise similarly to FIG. 3, the laser arrangement of FIG. 6 comprises an impedance adaptation circuit 16, which is formed as a termination impedance circuit of the electro-absorption modulator section 112 of the laser 11.

(27) Furthermore, the electrical line 14 is in the form of a flexible line with a flexible substrate 141 and conductor tracks 142 arranged thereon. The driver 13 can additionally be supplied via a voltage source 132 (supply voltage V.sub.TWA) and an RF termination coil 131. By using the photocurrent I.sub.photo, which, as explained above, corresponds to the direct current I*.sub.photo that is actually flowing to the driver 13 due to the existing blocking capacitance 163, an energy saving during operation of the driver 13 of V.sub.TWAI.sub.photo is achieved.

(28) The traveling wave amplifier in particular has more than one amplifier stage. Traveling wave amplifiers per se are known, however, and further explanations will therefore not be provided. However, it should be pointed out that the solution is not limited to the use of traveling wave amplifiers. An amplifier having only one amplifier stage could be used as the driver.

(29) Furthermore, FIG. 6 shows capacitances C.sub.in,term, C.sub.ext,EAM, C.sub.int and C.sub.ext,IC, via which an RF ground connection of the laser arrangement 1 (of the driver 13 and of the electro-absorption modulator section 112) is effected, wherein draining of the photocurrent I.sub.photo to ground is prevented, however. On the output side with respect to the returning waves, the driver 13, to which an input signal V.sub.RFIN is supplied, comprises a termination network with a resistance R.sub.out,term and capacitances C.sub.out,term, C.sub.out,ext. For the rest, reference is made to the explanations in relation to FIG. 4.

(30) FIG. 7 shows a variant of FIG. 6, which is similar to FIG. 4 and according to which the impedance adaptation circuit 16 is formed without the direct current blocking capacitance 163. This reduces the manufacturing steps required to produce the electro-absorption modulator section 112. It is additionally conceivable that the driver-side voltage source 132 (V.sub.TWA) is dispensed with.

(31) FIG. 8 relates to a further variant of the laser arrangement 1 according to the solution, according to which the impedance adaptation circuit 16 is not formed as a termination impedance circuit but is integrated in the electrical connection 14, which is formed as a flexible line. Accordingly, adaptation inductances 161a, 161b (L.sub.flex,a, L.sub.flex,b), adaptation resistances 162a, 162b (R.sub.flex,a, R.sub.flex,b) and direct current blocking capacitances 163a, 163b (C.sub.flex,a, C.sub.flex,b) are arranged between the conductor tracks 142 of the electrical connection 14, in particular in the form of structures which are likewise arranged on the carrier 141 of the electrical connection 14 and here between the conductor tracks 142. It is conceivable that the photocurrent I.sub.photo generated is supported via the adaptation resistance 162. It is also possible that, with respect to the electrical connection 14, a potential is used (to which for example the external ones of the conductor tracks are connected) which is higher than the ground of the driver 13, and draining of part of the photocurrent via the adaptation resistance 162 is thus counteracted.

(32) Among the inductance, resistance and capacitance structures L.sub.flex,a, L.sub.flex,b, R.sub.flex,a, R.sub.flex,b, C.sub.flex,a, C.sub.flex,b in each case one is situated between two adjacent conductor tracks 142, wherein the structures together produce a total adaptation inductance, a total adaptation resistance and a total blocking capacitance. The inductance, resistance and capacitance structures L.sub.flex,a, L.sub.flex,b, R.sub.flex,a, R.sub.flex,b, C.sub.flex,a, C.sub.flex,b are located on a half, which faces the laser 11 (in particular the electro-absorption modulator section 112), of the electrical connection 14 (in particular in the region of an end of the electrical connection 14 facing the electro-absorption modulator section 112).

(33) The embodiment of FIG. 9 corresponds to that of FIG. 8, but wherein the RF termination coil 131 that is coupled to the driver 13 is dispensed with. Accordingly, a supply voltage V*.sub.TWA is supplied here to the traveling wave amplifier using a parallel capacitance C.sub.out, ext via an adaptation resistance R.sub.out, term. The capacitance C.sub.out,ext together with a further capacitance C.sub.out,term realizes a broadband RF connection of the adaptation resistance R.sub.out,term to ground. The energy saving for the supply of the drive is determined by V*.sub.TWAI*.sub.photo, wherein V*.sub.TWA=V.sub.TWA+R.sub.out,termI*.sub.TWA, I.sub.TWA=I.sub.TWA.

(34) According to the embodiment of FIG. 10, the separate voltage source 132 for the additional supply of the driver 13 is also dispensed with; that is to say the driver 13 is supplied solely by way of the photocurrent generated in the electro-absorption modulator section 112 of the laser 11, wherein optionally in addition to the photocurrent the current flowing through the resistance R.sub.flex can serve for supplying the driver 13. It is conceivable herefor that the capacitance C.sub.flex is dispensed with.

(35) It is pointed out that elements of the embodiments described above can of course also be used in combination with one another. The solution is furthermore, as already mentioned above, not limited to a hybrid construction of the laser arrangement. In particular, the above-described embodiments can similarly also be realized with a monolithic construction of the laser arrangement.