GB2400233A - Distributed feedback laser device - Google Patents
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- GB2400233A GB2400233A GB0307491A GB0307491A GB2400233A GB 2400233 A GB2400233 A GB 2400233A GB 0307491 A GB0307491 A GB 0307491A GB 0307491 A GB0307491 A GB 0307491A GB 2400233 A GB2400233 A GB 2400233A
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- 230000008878 coupling Effects 0.000 claims abstract description 43
- 238000010168 coupling process Methods 0.000 claims abstract description 43
- 238000005859 coupling reaction Methods 0.000 claims abstract description 43
- 230000003287 optical effect Effects 0.000 claims description 10
- 230000000694 effects Effects 0.000 description 14
- 230000005540 biological transmission Effects 0.000 description 12
- 230000008033 biological extinction Effects 0.000 description 8
- 238000010586 diagram Methods 0.000 description 8
- 230000004044 response Effects 0.000 description 7
- 230000008859 change Effects 0.000 description 6
- 238000001228 spectrum Methods 0.000 description 6
- 230000003247 decreasing effect Effects 0.000 description 3
- 239000000835 fiber Substances 0.000 description 3
- 238000011835 investigation Methods 0.000 description 3
- 238000002310 reflectometry Methods 0.000 description 3
- 230000003595 spectral effect Effects 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 239000013307 optical fiber Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000002939 deleterious effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000000059 patterning Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
- H01S5/042—Electrical excitation ; Circuits therefor
- H01S5/0425—Electrodes, e.g. characterised by the structure
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
- H01S5/1228—DFB lasers with a complex coupled grating, e.g. gain or loss coupling
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/0618—Details on the linewidth enhancement parameter alpha
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/062—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes
- H01S5/0625—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes in multi-section lasers
- H01S5/06253—Pulse modulation
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/062—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes
- H01S5/0625—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes in multi-section lasers
- H01S5/06255—Controlling the frequency of the radiation
- H01S5/06258—Controlling the frequency of the radiation with DFB-structure
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- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Optics & Photonics (AREA)
- Semiconductor Lasers (AREA)
- Optical Communication System (AREA)
Abstract
The performance of a 'push-pull' DFB laser is significantly improved by designing the grating 20 to have a <WC 1>complex coupling coefficient comprising a significant imaginary component.
Description
DISTRIBUTED FEEDBACK LASER DEVICE
The present invention relates to semiconductor lasers, and in particular to distributed feedback lasers having two or more electrical contacts.
So-called 'push-pull' lasers are known from US 5 502 741 and US 5 901 164. Push-pull lasers are formed by dividing the top electrode into one or more sections. Current can then be applied to the electrodes. In the case of a laser having two electrodes, the output of the laser will be in one state when a current of I+AI is applied to the first electrode and I-AI is applied to the second electrode: when a current of I-AI is applied to the first electrode and I+AI is applied to the second electrode then the output of the laser will be in a second state. The difference between these two states enables a 'push-pull' laser to be used as a transmitter in am optical communications system.
Figure 1 shows a schematic depiction of a 'push-pull' laser.
The laser 100 is essentially a distributed feedback laser and as such comprises an active region 10 and a grating 20.
Additionally, two electrodes 30 and 40 are formed on the top surface of the laser (these may be formed separately or a single electrode may be formed and then divided into two different regions). Application of current to the electrodes causes light to be emitted from the active region 10 of the laser.
In theory, because a 'push-pull' laser is being switched from 30020158 GB;doc - 2 a state with most of the optical power at one end of the laser to a symmetric state with most of the power at the other end of the laser, it should be possible to operate push-pull' lasers at greater data rates than conventional distributed feedback lasers (DFBs), which require switching from 'off' to 'on' in order to operate them.
Another significant advantage of 'push-pull' lasers is that their output has very low levels of chirp compared to a conventional DFB laser and thus 'push-pull' lasers should be operable at higher bit-rates before dispersion effects limit transmissions. Figures 2a and 2b show respectively the power and frequency response with time for a conventional DFB when two pulses are generated: Figures 2c and 2d show the equivalent responses for a 'push-pull' laser when to pulses are generated. It can be seen clearly that the variation of frequency for the conventional DFB is significantly greater than for the 'push-pull' laser.
In order to provide a comparable low-chirp optical source, it would be necessary to integrate a DFB laser with an electro- absorption modulator (EAM). The use of a 'push-pull' DFB (PPDFB), in comparison, requires simpler fabrication processes using more established techniques, obviates the need for critical wavelength alignment with the modulator and adjustment of the mean bias current and provides significantly higher output power.
However, a number of problems with 'push-pull' lasers have been reported which prevent reliable high data rate operation that would enable their use in telecommunications networks: 30020158 GB.doc - 3 À the extinction ratio is lower than is typically acceptable, i.e. in the region of 6-lOdB (typical DFB extinction ratios are in the region of 20dB À measurements made on 'push-pull' lasers have indicated that the actual bandwidth that can be realised is typically 10-30% less than that of an equivalent DFB laser, rather than 3-5 time greater, as was predicted by initial modelling work. It is believed that this effect is due to the absence of the electron-photon resonance peak in 'push-pull' lasers, which allows the underlying electron lifetime to become prominent.
À some 'push-pull' lasers have a tendency to develop severe patterning effects, in which the laser occasionally transmits a range of spurious modes in response to particular data patterns.
According to a first aspect of the invention there is provided a distributed feedback laser device comprising an active region and a grating and two or more electrical contacts, whereby the application of a first electrical signal to the first electrical contact and a second electrical signal to the second electrical contact causes the laser device to generate a first optical signal, and whereby the application of the first electrical signal to the second electrical contact and the second electrical signal to the first electrical contact causes the laser device to generate a second optical signal, the laser device being characterized in that the grating has a coupling coefficient comprising a significant imaginary component.
30020158 GB.doc - 4 Conventionally, the grating coupling coefficient is selected so as to be non-complex, that is the imaginary component is zero. Typical process control means that the very worst case imaginary component that could be expected would be less than +O.lj cm1. In the context of the present invention, a significant imaginary component is +lj cm1.
The imaginary component of the coupling coefficient and the real component of the coupling coefficient may both have a positive value. "Positive" and "negative" in terms of diffraction gratings are defined here to imply that regions of increased refractive index within the laser correspond to regions of increased gain.
The value of the imaginary component of the coupling coefficient may be between 1 cm1 and 20 cm1, or alternatively the value of the imaginary component of the coupling coefficient may be substantially 1% to 15% of the value of the real component of the coupling coefficient.
The value of the real component of the coupling coefficient may be between 50 cm1 and 100 cm1. The value of the real component of the coupling coefficient may be between 80 cm and 90 cm1 and the value of the imaginary component of the coupling coefficient may be between 1 cm1 and 10 cm1. In an embodiment the value of the real component of the coupling coefficient is around 85 cm1 and the value of the imaginary component of the coupling coefficient is around 6 cm1.
The invention will now be described, by way of example only, with reference to the following Figures in which: 30020158 GB.doc Figure 1 shows a schematic depiction of a 'push-pull' laser; Figure 2 shows a graphical depiction of a comparison between the performance of a conventional DFB and a push-pull' laser; Figure 3 shows a graphical depiction comparing the bandwidth of a conventional DFB and a 'push-pull' laser; Figure 4 shows a similar bandwidth response to Figure 3, with the bias current reduced to 30mA; Figure 5 shows the effects of increasing the bias current on bandwidth for a conventional DFB and a push-pull' laser; Figure 6 shows the effects of increasing the K value on bandwidth for the 'push-pull' laser; Figure 7 shows effects of increasing the length of the active region on bandwidth for the 'push-pull' laser; Figure 8 shows a graphical depiction comparing the bandwidth of a DFB and an optimised 'push-pull' laser; Figure 9 shows a graphical depiction of eye diagrams show for the optimised 'push-pull' laser; Figure 10 shows a graphical depiction of frequency and power variation with time for the optimised 'push-pull' laser; Figure 11 shows a graphical depiction of frequency and power variation with time for a 'push-pull' laser having a coupling coefficient in which the real and imaginary components have different signs; Figure 12 shows a graphical depiction of the stability of a 'push-pull' laser having a non-complex coupling 30020158 GB.<loc - 6 coefficient; Figure 13 shows a graphical depiction of the stability of a 'push-pull' laser having a coupling coefficient comprising a negative complex component; Figure 14 shows a graphical depiction of the stability of a 'push-pull' laser having a coupling coefficient comprising a negative complex component; Figure 15 shows a graphical depiction of the variation of bandwidth for different 'push- pull' lasers; Figure 16 shows a graphical depiction of the change in transmission eye for different 'push-pull' lasers; Figure 17 shows a graphical depiction of the change in chirp for different 'push-pull' lasers; Figure 18 shows a graphical depiction of the transmission eye, chirp and power output for an optimised 'push-pull' laser; Figure 19 shows a graphical depiction of the transmission eye, chirp and power output for a DFB-EAM; and Figure 20 shows a graphical depiction of the measured wavelength spectrum for a 'push-pull' laser device operated at 2. 5Gb/s.
Figure 1 shows a schematic depiction of a PPDFB. In order to change the characteristics of its optical outputs, there are a range of parameters that can be controlled: the coupling coefficient of the grating, K, and the length of the active region, L, which are often considered as a dimensionless product KL that can characterize the active region of the laser; the bias currents applied to the laser; the driver 30020158 GB.doc - 7 circuits for the RF signals that will modulate the laser; the internal absorption of the laser, the linewidth enhancement factor, the gain saturation of the laser and the phase and reflectivity characteristics of the facets.
The investigation into improving the characteristics of PPDFBs began by modelling the theoretical effects of modifying various parameters. Two different theoretical models were used and the results showed a significant correlation.
A baseline for performance was set by modelling a PPDFB laser having a K of 45 cm1, two electrical contacts of 350pm length and a bias current of 35mA. Figure 3 shows a graphical depiction of the bandwidth of such a device (shown by a solid line), along with the bandwidth of a similar DFB having a single electrical contact (shown by a dotted line).
The surprising results, which are contrary to reported results, is that the PPDFB has significantly lower 3dB bandwidth, around 2.5 GHz, than a conventional DFB (around llGHz).
Figure 4 shows a similar bandwidth response, but in this case the bias current for both simple DFB and push-pull DFB laser has been reduced to 30mA and the coupling coefficient now has a significant complex component, having a value of 57+4j cm for both devices. Figure 4 shows that these changes have increased the bandwidth of the PPDFB to approximately llGhz, whilst the bandwidth of the conventional DFB remains substantially unchanged at around llGHz.
30020158 GB.doc Further modelling has shown that changing other variables has a less significant impact on device performance: reducing the value of epsilon, s, (often referred to as the non-linear gain parameter) by a factor of ten caused a increase in bandwidth, as is predicted in the literature, but the effect was marginal. In this case non-linear gain, G. is related to linear gain, Go' by the equation G= Go l+aS where S is the photon density in cm1 and a typical value of s would be 3 x 1017 cm3.
Altering the material linewidth enhancement factor (also referred to as Henry's a) shows that increased a values led to an increase in bandwidth. This is believed to be due to small carrier density fluctuations causing increased changes in refractive index for a given change in carrier density.
This in turn causes increased changes in grating reflectivity which 'push' the peak photon density within the laser from end-to-end more rapidly.
Figure 5 shows the effects of increasing the bias current.
The solid line shows the bandwidth for the device using a standard bias current, the dotted line shows the bandwidth of the device using 50% more bias current and the dashed line shows the bandwidth of the device using twice the standard bias current. Figure 6 shows the effects of increasing the K value for the PPDFB: a 50% increase (dotted line) gives rise to an increase in bandwidth of approximately 25GHz, but a further increase (dashed line, representing a 100% increase 30020158 GB.doc over the base value) causes the mode spacing to be reduced, increasing resonance within the laser and a consequent decrease in bandwidth. Figure 7 shows a similar trend for increasing the length of the active region: a 600pm long device has a bandwidth of about 12GHz; a 700pm long device has an increased bandwidth of about 25GHz whilst increasing the device length to 800pm causes the bandwidth to decrease.
Further investigations have led to the selection of a set of parameters that provide maximum bandwidth without causing unwanted, deleterious effects to other aspects of the laser's performance. Compared with the device discussed above in relation to Figure 4, the optimised device has a bias current of 60mA and a coupling coefficient of 85+6j cml. Figure 8 shows the bandwidth characteristic for this device (shown by he solid line), which has a bandwidth of approximately 28GHz.
The same device having a single electrical contact has a bandwidth of around 14GHz and is shown by a dotted line.
Analysis of eye diagrams show that the optimised PPDFB has a superior eye diagram (see Figure 9b) when compared with the original PPFB having a complex coupling coefficient (see Figure 9a). It can also be seen from Figure 9c that the eye diagram for the optimised PPFB remains open after transmission over 40km of standard optical fibre (assuming a lasing wavelength of around 1500 nm and thus a dispersion figure of 17ps/nm/km).
The use of a complex coupling coefficient is believed to be novel for a push-pull laser and further investigation into the range of coupling coefficients that provide the beneficial results was undertaken. It was found that the 30020158 GB.doc positive results were only obtained when the real and imaginary components of the coupling coefficient, (KRe and KIm respectively) were positive. The reason or this is that the gain maxima of the grating coincide with the refractive index maxima, such that the grating provides in-phase gain, leading to the laser transmitting in a single mode on the long wavelength side of the Bragg stop band. Figure lea shows the associated frequency spectrum of the laser output and Figure lob shows the power variation with time for the laser, which shows that the laser settles into a steady-state condition in an acceptably short period of time.
In contrast Figures lla and llb show the same characteristics for a 'pushpull' laser having a coupling coefficient in which the real and imaginary components have different signs.
In this case the grating is anti-phase and causes the laser to selfpulsate, leading to the highly unsatisfactory traces which are shown in Figure 11.
Figure 12 shows modelled evidence that a non-complex coupling coefficient can also be the cause of problems for 'push-pull' lasers. The three dimensional graph shows the variation of wavelength with time for the output of a 'push-pull' laser where the coupling coefficient of the laser is slowly scanned from 0 at time zero to 80 cm1, while the laser is modulated with a 101010101... data pattern using a 10 Gbit/s NRZ transmission scheme. Figure 13 shows a similar characteristic for a laser where the coupling coefficient of the laser is scanned from 20-j cm1 to 80-j cm1 and again there are significant levels of spectral instability. Figure 14 shows the same characteristic for a 'push-pull' laser 30020158 GB.doc having a coupling coefficient scanned from 20+j cm1 to 80+jcm1 and the spectrum remains narrow and single-moded over the range of interest. Increasing the value of K:m leads to an increase in the degree of spectral stability over time. The other significant effect of increasing KIm is that the resonance peak is damped, resulting in decreased bandwidth. However, this effect is minimal over the range of interest with a change from 85+2jcm1 to 85+10jcm1 resulting in a decrease in bandwidth from 25GHz to 22GHz. This increase in the value of KIm has a negligible effect on the extinction ratio and causes a 50% decrease in maximum chirp.
Increasing the value of KIm also results in a more open eye for lOGb/s transmission over 40km of standard fibre.
The effect of altering the internal attenuation of the PPDFB was also modelled. Figure 15 shows the variation of bandwidth with device attenuation and Figures 16 and 17 show graphs depicting the change in transmission eye after 40 km of standard fibre and chirp respectively, for attenuation values of 7.5cm1 (Figures 16a & 16b), 15cml (Figures 17a & 17b) and 30cm1 (Figures 18a & lab). The increase in loss appears to cause a minor decrease in bandwidth and an increase in chirp. Interestingly, the received eye quality appears to be at a maximum for an attenuation value of 15cml, with decreased eye quality at both 7.5cm1 and 30cml.
Further modelling work was undertaken in order to compare the performance of a PPDFB with a combination of a conventional DFB and an EAM. In these cases, the performance of a conventional lOGB/s driver circuit was used, that has a total 30020158 GB.doc drive current of 60mA with 55mA peak-to-peak modulation current. The assumed facet (power) reflectivity is 0.1% and the coupling coefficient is 85+6j emu. Figure 18 shows the eye diagrams for the PPDFB for back-to-back configuration (Figure 18a), and after 40 and 60km of standard fibre (Figures 18b and 18c respectively). It appears from Figure 18c that the transmission limit for the PPDFB is about 60 65km. The extinction ratio after 40km of transmission is 6dB which, while being less than the extinction ratios provided by other optical transmitters, is believed to be adequate.
Figure 18d shows the spectrum generated by a number of pulses of the laser and Figure 18e shows the associated chirp response.
Figure 19 shows the equivalent graphs for a DFB-EAM that has been configured to provide an extinction ratio of lOdB at a data rate of lOGb/s, with a peak output power of 5mW. Figure 19a shows the eye diagrams for the device when connected back-to-back and Figure l9b shows the eye diagrams after 40km of transmission over optical fibre. Figure l9c shows the variation in power for two pulses and Figure led shows the chirp response associated with the power spectrum shown in Figure l9c. Comparison of Figures 18 and 19 show that the PPDFB has significantly superior chirp performance (almost a degree of magnitude better) than the DFB-EAM and that the received eye after 40km of transmission for the DFB-EAM show very considerable degradation.
It appears from the modelling work described above that designing a pushpull DFB laser to comprise a coupling coefficient having a significant imaginary component leads to 30020153 GB.doc - 13 a significant increase in device performance, to a level that is superior to that of equivalent optical transmitters in some regards (for example, low chirp levels, quality of eye diagram, etc.) whilst appearing to have overcome some of the drawbacks conventionally associated with push-pull devices (low extinction ratios, for example).
Some experimental work has been undertaken to validate the theoretical results presented above. A wafer comprising DFBs designed to operate at lOGb/s was processed conventionally using a ternary quantum well etch such that the grating was defined so as to have a complex coupling coefficient in the range KRe = 50-100 cml and KIm = 2-10 cm1 and the electrical contact was divided into two regions. The devices were measured and it was found that approximately 95% of them lased on the long wavelength side of the Bragg stop band, which is desirable for a push-pull laser and also what is expected from modelling lasers with complex gratings as described above.
A sample wavelength spectrum is shown in Figure 20, which was obtained by modulating the device at 2.5Gb/s at elevated temperatures such that an extinction ratio of 8dB is obtained at temperatures of 85 C. The -20dB spectral linewidth is decreased from 0.44 nm while operating the laser in a conventional DEB mode to 0.29nm when operating in push-pull mode.
30020158 GR.doc - 14
Claims (7)
1. A distributed feedback laser device comprising an active region and a grating and two or more electrical contacts, whereby the application of a first electrical signal to the first electrical contact and a second electrical signal to the second electrical contact causes the laser device to generate a first optical signal, and whereby the application of the first electrical signal to the second electrical contact and the second electrical signal to the first electrical contact causes the laser device to generate a second optical signal, the laser device being characterized in that the grating has a coupling coefficient comprising a significant imaginary component.
2. A distributed feedback laser according to claim 1, wherein the imaginary component of the coupling coefficient and the real component of the coupling coefficient both have a positive value.
3. A distributed feedback laser according to claim 1, wherein the value of the imaginary component of the coupling coefficient is between 1 and 20 cml.
4. A distributed feedback laser according to claim 1, wherein the value of the imaginary component of the coupling coefficient is substantially 1% to 15% of the value of the real component of the coupling coefficient.
5. A distributed feedback laser according to any preceding 30020158 GB.doc - 15 claim, in which the value of the real component of the coupling coefficient is between 50 and 100 cm1.
6. A distributed feedback laser according to any preceding claim, in which the value of the real component of the coupling coefficient is between 80 and 90 cm1 and the value of the imaginary component of the coupling coefficient is between 1 and 10 cm1.
7. A distributed feedback laser according to claim 6, in which the value of the real component of the coupling coefficient is around 85cm1 and the value of the imaginary component of the coupling coefficient is around 6cml.
30020158 GB.doc
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| Application Number | Priority Date | Filing Date | Title |
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| GB0307491A GB2400233B (en) | 2003-04-01 | 2003-04-01 | Distributed feedback laser device |
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| Application Number | Priority Date | Filing Date | Title |
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| GB0307491A GB2400233B (en) | 2003-04-01 | 2003-04-01 | Distributed feedback laser device |
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| GB0307491D0 GB0307491D0 (en) | 2003-05-07 |
| GB2400233A true GB2400233A (en) | 2004-10-06 |
| GB2400233B GB2400233B (en) | 2006-05-10 |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5502741A (en) * | 1994-03-22 | 1996-03-26 | Northern Telecom Limited | Direct amplitude modulation of lasers |
| US5506859A (en) * | 1995-02-16 | 1996-04-09 | At&T Corp. | Article comprising a DFB laser with loss coupling |
| EP0903820A2 (en) * | 1997-09-18 | 1999-03-24 | Nortel Networks Corporation | Two-section complex coupled distributed feedback semiconductor laser with enhanced wavelength tuning range |
| EP1137133A1 (en) * | 2000-02-25 | 2001-09-26 | Lucent Technologies Inc. | Quantum cascade laser having distributed feedback for single-mode cw operation |
-
2003
- 2003-04-01 GB GB0307491A patent/GB2400233B/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5502741A (en) * | 1994-03-22 | 1996-03-26 | Northern Telecom Limited | Direct amplitude modulation of lasers |
| US5506859A (en) * | 1995-02-16 | 1996-04-09 | At&T Corp. | Article comprising a DFB laser with loss coupling |
| EP0903820A2 (en) * | 1997-09-18 | 1999-03-24 | Nortel Networks Corporation | Two-section complex coupled distributed feedback semiconductor laser with enhanced wavelength tuning range |
| EP1137133A1 (en) * | 2000-02-25 | 2001-09-26 | Lucent Technologies Inc. | Quantum cascade laser having distributed feedback for single-mode cw operation |
Non-Patent Citations (2)
| Title |
|---|
| "High single-mode stability gain-coupled DFB laser for new applications"; Makino, T.; Communications, 1999. APCC/OECC '99. Fifth Asia-Pacific Conference on ... and Fourth Optoelectronics and Communications Conference , Vol 2, 18-22 Oct 1999; Pages: 1315 -1319 vol.2 * |
| "High speed direct modulation of diode lasers: towards terabit communications" Flanigan, B.J.; Carroll, J.E.; Towards Terabit Transmission, IEE Colloquium on , 19 May 1995, Pages 1/1 -1/6 * |
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| Publication number | Publication date |
|---|---|
| GB0307491D0 (en) | 2003-05-07 |
| GB2400233B (en) | 2006-05-10 |
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