Two VCSELs placed facing each other with one biased chip while the second chip is unbiased is sho... more Two VCSELs placed facing each other with one biased chip while the second chip is unbiased is shown as a promising alternative to the popularly used conventional SESAM mode-locked VECSEL to generate mode-locked pulses. We propose a theoretical model using time-delay differential rate equations and numerically show that the proposed dual-laser configuration functions as a typical gain-absorber system. Parameter space defined by laser facet reflectivities and current are used to show general trends in the exhibited nonlinear dynamics and pulsed solutions.
We report modelocking rates of up to 620 GHz from what is, to our knowledge, the first purpose fa... more We report modelocking rates of up to 620 GHz from what is, to our knowledge, the first purpose fabricated monolithic compound cavity mode locked (CCM) laser diodes at 0.86 μm. The experiments here were performed with 3-section GaAs-AlGaAs double quantum-well ridge-waveguide laser diodes, incorporating a saturable absorber and two gain sections, with an etched reflector between them
2013 15th International Conference on Transparent Optical Networks (ICTON), 2013
This work presents an overview of a combined experimental and theoretical analysis on passive mod... more This work presents an overview of a combined experimental and theoretical analysis on passive mode-locking in semiconductor quantum-well lasers based on reverse biased saturable absorbers. The experimental results describe the dynamics of laser diodes based on Aluminum quaternary materials at 1550 nm and we will also mention recent results related to GaAs Lasers at 830 nm. The experimental facts evidenced the important impact of the dispersion in frequency domain of the saturable absorption as well as the relevance of the dynamical detuning between the gain peak of the amplifying sections and the edge of absorption of the saturable absorber. Reproducing the dispersion of the saturable absorption demanded an important effort on our modeling approach, specially regarding the development of an efficient but reasonably accurate method to describe in time domain the response of the semiconductor material. The successful realization of this endeavor resulted in the development of the free software simulation package FreeTWM that allows to simulate a large class of multi-section devices. I will discuss how our modeling approach reproduces and explains the experimental results. I will conclude on a discussion of the possible improvements to FreeTWM as for instance the consideration of the ultrafast non linearities e.g. the so-called spectral hole burning and carrier heating effects.
The authors have analysed optoelectronic or all-optical frequency conversion in the range from hu... more The authors have analysed optoelectronic or all-optical frequency conversion in the range from hundreds of MHz up to hundreds of GHz using Q-switched and mode locked laser diodes. Subcarrier modulation was considered as an example of possible applications. The advantages of a mode locked scheme, besides higher achievable frequencies, include flat frequency dependence of the conversion efficiency at frequencies below the electron-photon resonance and higher stability of the local oscillator frequency, whereas the advantage of Q-switching is relatively smaller modulation of output light at the signal frequency.
ABSTRACT We discuss current and potential problems in theory and numerical modelling of monolithi... more ABSTRACT We discuss current and potential problems in theory and numerical modelling of monolithic mode-locked semiconductor lasers, present some recent advances in the field and compare advantages and shortcomings of time- and time-frequency domain modelling approaches.
A time-frequency-domain formalism for analysis of mode-locked quantum dot laser dynamics is devel... more A time-frequency-domain formalism for analysis of mode-locked quantum dot laser dynamics is developed. A potential for generating subpicosecond pulses in an actively mode-locked construction is predicted. Low chirp pulses are predicted, correlating with a low linewidth enhancement factor calculated. Strong hole burning associated with quantum dot active media is shown to broaden the mode-locking spectra noticeably, leading to shorter pulses.
2008 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD), 2008
ABSTRACT A numerical study of the influence of optical feedback on the dynamics of high-bit-rate ... more ABSTRACT A numerical study of the influence of optical feedback on the dynamics of high-bit-rate mode-locked laser diodes is presented. A wide variety of dynamic regimes is discovered, which is qualitatively different to both single-frequency and self-pulsing lasers. The relation of the findings to the recent experimental results is discussed, and the potential of absorber-amplifier modules as optical isolators investigated.
Proceedings of the 4th International Conference on Numerical Simulation of Optoelectronic Devices, 2004. NUSOD '04.
ABSTRACT This study proposes a new, simplified delay-differential approach intended at simulating... more ABSTRACT This study proposes a new, simplified delay-differential approach intended at simulating the device properties at high bias, when the diffusion is not significant and can be neglected. This formalism is free from the limitations of the drift-diffusion method, and at the same time offers a qualitative increase in the computational efficiency, which makes it attractive for use as a part of complex simulation procedures for modelling and optimisation of realistic device dynamic behaviour, and thus potentially for implementation in efficient device simulators.
Conference Proceedings LEOS'96 9th Annual Meeting IEEE Lasers and Electro-Optics Society
We report spectral collapse and self-sustained pulsations observed in the InGaAs-GaAs ridge waveg... more We report spectral collapse and self-sustained pulsations observed in the InGaAs-GaAs ridge waveguide laser diodes emitting at 0.98 μm, and discuss the possible origin of these effects
ABSTRACT The effect of electrical (finite absorber response time) and optical (distant reflector)... more ABSTRACT The effect of electrical (finite absorber response time) and optical (distant reflector) external effects on the performance of monolithic mode-locked lasers in a monolithically integrated environment is discussed and illustrated using numerical modeling. The relation of the findings to the recent experimental results is discussed, and some methods of reducing the feedback effects are assessed.
Abstract The chapter reviews the recent advances and the state of the art in the area of mode-loc... more Abstract The chapter reviews the recent advances and the state of the art in the area of mode-locked semiconductor lasers. Starting with the principles and theoretical foundations of mode-locked semiconductor laser operation, the chapter reviews the recent advances in, and the modern state of, the mode-locked semiconductor theory, summarizing the main theoretical predictions and discussing the effects of the operating point and the main laser parameters on the laser performance. We proceed with reviewing recent experimental advances, showing how physical reasoning and theoretical predictions inform the strategies of improving the laser performance as regards output and peak power, pulse duration, repetition rate range, and jitter. The chapter discusses the recent novel paradigms of mode locking (ML) in semiconductor lasers, such as the use of low-dimensional materials, coherent saturable absorption effects, and self ML without a saturable absorber. The chapter concludes with a brief overview of prospective applications.
ABSTRACT A general theory of multichannel coherent particle escape introducing the escape matrix ... more ABSTRACT A general theory of multichannel coherent particle escape introducing the escape matrix based on the scattering formalism has been developed and applied to the problem of hole escape from biased quantum wells. This approach incorporates band-mixing effects, such as valence-band nonparabolicity and heavy-to-light (light-to-heavy) hole transformations, in the theory of carrier escape from quantxum wells consistently with the principles of multiband effective-mass theory. The numerical calculations, made in the Luttinger approximation, show significant influence of the band-mixing effects on the hole escape time and are in satisfactory agreement with available experimental data. The effective decrease of the heavy-hole tunneling mass (“lightening”) as a result of the light-hole admixture is found to be the major reason for the escape-time decrease, as compared to the simple parabolic-band effective-mass model. The concept of the escape matrix can be used for investigating multichannel coherent escape processes in different systems such as quantum wires, quantum dots, or photonic structures.
Threshold properties and pulsed output of AlGaInP visible-emitting lasers with an asymmetric wave... more Threshold properties and pulsed output of AlGaInP visible-emitting lasers with an asymmetric waveguide structure and a bulk active layer are analysed. The effects of the current leakage, increased by the heating of the laser due to the proximity of the electrical pulse source and the Joule heating in and around this source are analysed. When optimising the laser design, waveguiding properties of the bulk active layer are shown to be important, leading to threshold currents decreasing, and injection efficiency increasing, with active layer thickness in lasers with moderately thick (< 0.1 µm) active layers. Catastrophic optical degradation is shown to set an upper limit to the optimal active layer thickness.
A semiconductor laser design for efficient, high power, high brightness red light emission is pro... more A semiconductor laser design for efficient, high power, high brightness red light emission is proposed, using a large optical cavity asymmetric waveguide and a bulk active layer (AL) positioned very close to the p-cladding. The low threshold carrier density associated with the broad AL, as well as the proximity of the AL to the p-cladding, ensure that the electron leakage current, the major detrimental factor in red lasers, stays modest in a broad range of excitation levels. This in turn promises high-power, efficient operation.
2020 22nd International Conference on Transparent Optical Networks (ICTON), 2020
InGaAsP/InP high pulsed power lasers operating in the range of $1.3 - 1.6\ \mu \mathrm{m}$ have b... more InGaAsP/InP high pulsed power lasers operating in the range of $1.3 - 1.6\ \mu \mathrm{m}$ have been intensely studied recently, with LIDAR technology being the primary application. We present and analyse a design with a bulk active layer which has a large refractive index step with respect to the optical confinement layer and is located close to the $p$-cladding. It is shown that such lasers can allow a noticeable performance increase over the state of the art. The dependence of the laser performance on the design parameters including the thicknesses of the active layer and the waveguide, the cavity length, and the waveguide asymmetry, is analysed. It is shown that short cavity lengths (∼1 mm or even shorter) can be used in the design considered for achieving high pulsed power. Due to the significant waveguiding properties of the active layer, the use of both symmetric and asymmetric waveguide designs is possible, with only slightly higher output predicted for the asymmetric one. Both designs allow operation with a single, broad transverse mode enabling high brightness.
Semiconductor Lasers and Diode-based Light Sources for Biophotonics, 2018
We have attempted an overview of fast-pulsating lasers (gain-switched, Q-switched and mode-locked... more We have attempted an overview of fast-pulsating lasers (gain-switched, Q-switched and mode-locked) in various biomedical applications. By necessity, the accents in the chapter have been to an extent coloured by our research experience and interests; apologies are extended to those authors whose work may have been omitted. Different properties of a laser system are important for different applications (e.g., high instantaneous and average power for multiphoton spectroscopy vs. spectral tuning range for OCT), but all the designs above benefit from the properties of semiconductor lasers such as chip compactness, ease of pumping, and high gain per unit length. The use of nanostructures, particularly QDs, has been shown to open new exciting opportunities.
Semiconductor Lasers and Laser Dynamics VIII, 2018
Vertical External Cavity Surface Emitting Lasers (VECSELs) have been used for mode-locked operati... more Vertical External Cavity Surface Emitting Lasers (VECSELs) have been used for mode-locked operation by using a Semiconductor Saturable-Absorber Mirror (SESAM), usually in the external cavity [1] but also integrated in the gain-chip [2]. Impressive progress has been achieved since the first demonstration of an SESAM mode-locked VECSEL in terms of pulse duration, average optical power, and peak power. While the shortest pulses have been achieved with optically pumped active layers, electrically pumped structures are promising for a number of applications. Α versatile and accurate, if fairly complex, delay-differential theoretical model for mode-locking in electrically pumping VECSELs based on the physical description of gain and SESAM chips has been presented [3], however only the linear cavity geometry has been studied. A somewhat different approach was taken in [4][5] where an experiment-informed model representing the laser somewhat artificially as a sequence of gain, absorber, and dispersion elements in a unidirectional ring cavity (reminiscent of the classic Haus theory) was developed, and successfully reproduced the measured laser parameters in both pico-and femtosecond regimes. In the current work, we present a somewhat simplified model based on the physical laser design as in [3], which however can accommodate realistic geometry, both linear and folded-cavity. The model is applied to study different regimes of laser operation, including the possibility of colliding pulse mode locking at harmonics of the fundamental roundtrip frequency. As in [3], we base the derivation on the analysis of amplitudes of waves incident onto, and reflected from, elements of the laser cavity, using the amplitude of the field reflected from the “bulk” of the cavity as the dynamic variables for the description of light. Standard rate equations are used for carrier densities. In the case of a linear cavity the model is thus somewhat similar to that used in [3] though somewhat simplified. No matrices of the type used in [3] are needed to recalculate the dynamic variables in our simplified model. The use of phenomenological gain-carrier density dependences and linewidth enhancement factors, while less rigorous than the simplified microscopic model of [3], enables relatively easy inclusion of polarization dependences, allowing double-polarisation frequency comb generation to be simulated. In the case of a folded (Z-type) cavity either the gain chip or the SESAM chip can be positioned “inside” the cavity. The dynamic variables in the case of the gain chip in the middle are the fields reflected from the bulk of the gain chip in the directions of the output mirror and the absorber chip, and from the bulk of the SESAM back to the gain chip . In the case of the gain chip in the middle position, the difference in the dynamics of the saturation of the gain chip changes the pulse parameters and stability limits compared with the linear cavity, but there is no qualitative difference. In the case of the absorber section in the intracavity position, colliding pulse dynamics was simulated with a rational relation between the delay times. Further results will be presented at the conference. References [1] U. Keller, A. C. Tropper, Phys. Reports, 429, 67 (2006) [2] D.J.H.C. Maas et al., Appl Phys B, 88, 493 (2007) [3] J. Mulet and S. Balle, IEEE J. Quantum Electron., 41, 1148 (2005) [4] M. Hoffmann et al., Opt. Express 18, 10143 (2010) [5] O.Sieber et al., Appl.Phys.B., 113, 133-145 (2013)
Two VCSELs placed facing each other with one biased chip while the second chip is unbiased is sho... more Two VCSELs placed facing each other with one biased chip while the second chip is unbiased is shown as a promising alternative to the popularly used conventional SESAM mode-locked VECSEL to generate mode-locked pulses. We propose a theoretical model using time-delay differential rate equations and numerically show that the proposed dual-laser configuration functions as a typical gain-absorber system. Parameter space defined by laser facet reflectivities and current are used to show general trends in the exhibited nonlinear dynamics and pulsed solutions.
We report modelocking rates of up to 620 GHz from what is, to our knowledge, the first purpose fa... more We report modelocking rates of up to 620 GHz from what is, to our knowledge, the first purpose fabricated monolithic compound cavity mode locked (CCM) laser diodes at 0.86 μm. The experiments here were performed with 3-section GaAs-AlGaAs double quantum-well ridge-waveguide laser diodes, incorporating a saturable absorber and two gain sections, with an etched reflector between them
2013 15th International Conference on Transparent Optical Networks (ICTON), 2013
This work presents an overview of a combined experimental and theoretical analysis on passive mod... more This work presents an overview of a combined experimental and theoretical analysis on passive mode-locking in semiconductor quantum-well lasers based on reverse biased saturable absorbers. The experimental results describe the dynamics of laser diodes based on Aluminum quaternary materials at 1550 nm and we will also mention recent results related to GaAs Lasers at 830 nm. The experimental facts evidenced the important impact of the dispersion in frequency domain of the saturable absorption as well as the relevance of the dynamical detuning between the gain peak of the amplifying sections and the edge of absorption of the saturable absorber. Reproducing the dispersion of the saturable absorption demanded an important effort on our modeling approach, specially regarding the development of an efficient but reasonably accurate method to describe in time domain the response of the semiconductor material. The successful realization of this endeavor resulted in the development of the free software simulation package FreeTWM that allows to simulate a large class of multi-section devices. I will discuss how our modeling approach reproduces and explains the experimental results. I will conclude on a discussion of the possible improvements to FreeTWM as for instance the consideration of the ultrafast non linearities e.g. the so-called spectral hole burning and carrier heating effects.
The authors have analysed optoelectronic or all-optical frequency conversion in the range from hu... more The authors have analysed optoelectronic or all-optical frequency conversion in the range from hundreds of MHz up to hundreds of GHz using Q-switched and mode locked laser diodes. Subcarrier modulation was considered as an example of possible applications. The advantages of a mode locked scheme, besides higher achievable frequencies, include flat frequency dependence of the conversion efficiency at frequencies below the electron-photon resonance and higher stability of the local oscillator frequency, whereas the advantage of Q-switching is relatively smaller modulation of output light at the signal frequency.
ABSTRACT We discuss current and potential problems in theory and numerical modelling of monolithi... more ABSTRACT We discuss current and potential problems in theory and numerical modelling of monolithic mode-locked semiconductor lasers, present some recent advances in the field and compare advantages and shortcomings of time- and time-frequency domain modelling approaches.
A time-frequency-domain formalism for analysis of mode-locked quantum dot laser dynamics is devel... more A time-frequency-domain formalism for analysis of mode-locked quantum dot laser dynamics is developed. A potential for generating subpicosecond pulses in an actively mode-locked construction is predicted. Low chirp pulses are predicted, correlating with a low linewidth enhancement factor calculated. Strong hole burning associated with quantum dot active media is shown to broaden the mode-locking spectra noticeably, leading to shorter pulses.
2008 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD), 2008
ABSTRACT A numerical study of the influence of optical feedback on the dynamics of high-bit-rate ... more ABSTRACT A numerical study of the influence of optical feedback on the dynamics of high-bit-rate mode-locked laser diodes is presented. A wide variety of dynamic regimes is discovered, which is qualitatively different to both single-frequency and self-pulsing lasers. The relation of the findings to the recent experimental results is discussed, and the potential of absorber-amplifier modules as optical isolators investigated.
Proceedings of the 4th International Conference on Numerical Simulation of Optoelectronic Devices, 2004. NUSOD '04.
ABSTRACT This study proposes a new, simplified delay-differential approach intended at simulating... more ABSTRACT This study proposes a new, simplified delay-differential approach intended at simulating the device properties at high bias, when the diffusion is not significant and can be neglected. This formalism is free from the limitations of the drift-diffusion method, and at the same time offers a qualitative increase in the computational efficiency, which makes it attractive for use as a part of complex simulation procedures for modelling and optimisation of realistic device dynamic behaviour, and thus potentially for implementation in efficient device simulators.
Conference Proceedings LEOS'96 9th Annual Meeting IEEE Lasers and Electro-Optics Society
We report spectral collapse and self-sustained pulsations observed in the InGaAs-GaAs ridge waveg... more We report spectral collapse and self-sustained pulsations observed in the InGaAs-GaAs ridge waveguide laser diodes emitting at 0.98 μm, and discuss the possible origin of these effects
ABSTRACT The effect of electrical (finite absorber response time) and optical (distant reflector)... more ABSTRACT The effect of electrical (finite absorber response time) and optical (distant reflector) external effects on the performance of monolithic mode-locked lasers in a monolithically integrated environment is discussed and illustrated using numerical modeling. The relation of the findings to the recent experimental results is discussed, and some methods of reducing the feedback effects are assessed.
Abstract The chapter reviews the recent advances and the state of the art in the area of mode-loc... more Abstract The chapter reviews the recent advances and the state of the art in the area of mode-locked semiconductor lasers. Starting with the principles and theoretical foundations of mode-locked semiconductor laser operation, the chapter reviews the recent advances in, and the modern state of, the mode-locked semiconductor theory, summarizing the main theoretical predictions and discussing the effects of the operating point and the main laser parameters on the laser performance. We proceed with reviewing recent experimental advances, showing how physical reasoning and theoretical predictions inform the strategies of improving the laser performance as regards output and peak power, pulse duration, repetition rate range, and jitter. The chapter discusses the recent novel paradigms of mode locking (ML) in semiconductor lasers, such as the use of low-dimensional materials, coherent saturable absorption effects, and self ML without a saturable absorber. The chapter concludes with a brief overview of prospective applications.
ABSTRACT A general theory of multichannel coherent particle escape introducing the escape matrix ... more ABSTRACT A general theory of multichannel coherent particle escape introducing the escape matrix based on the scattering formalism has been developed and applied to the problem of hole escape from biased quantum wells. This approach incorporates band-mixing effects, such as valence-band nonparabolicity and heavy-to-light (light-to-heavy) hole transformations, in the theory of carrier escape from quantxum wells consistently with the principles of multiband effective-mass theory. The numerical calculations, made in the Luttinger approximation, show significant influence of the band-mixing effects on the hole escape time and are in satisfactory agreement with available experimental data. The effective decrease of the heavy-hole tunneling mass (“lightening”) as a result of the light-hole admixture is found to be the major reason for the escape-time decrease, as compared to the simple parabolic-band effective-mass model. The concept of the escape matrix can be used for investigating multichannel coherent escape processes in different systems such as quantum wires, quantum dots, or photonic structures.
Threshold properties and pulsed output of AlGaInP visible-emitting lasers with an asymmetric wave... more Threshold properties and pulsed output of AlGaInP visible-emitting lasers with an asymmetric waveguide structure and a bulk active layer are analysed. The effects of the current leakage, increased by the heating of the laser due to the proximity of the electrical pulse source and the Joule heating in and around this source are analysed. When optimising the laser design, waveguiding properties of the bulk active layer are shown to be important, leading to threshold currents decreasing, and injection efficiency increasing, with active layer thickness in lasers with moderately thick (< 0.1 µm) active layers. Catastrophic optical degradation is shown to set an upper limit to the optimal active layer thickness.
A semiconductor laser design for efficient, high power, high brightness red light emission is pro... more A semiconductor laser design for efficient, high power, high brightness red light emission is proposed, using a large optical cavity asymmetric waveguide and a bulk active layer (AL) positioned very close to the p-cladding. The low threshold carrier density associated with the broad AL, as well as the proximity of the AL to the p-cladding, ensure that the electron leakage current, the major detrimental factor in red lasers, stays modest in a broad range of excitation levels. This in turn promises high-power, efficient operation.
2020 22nd International Conference on Transparent Optical Networks (ICTON), 2020
InGaAsP/InP high pulsed power lasers operating in the range of $1.3 - 1.6\ \mu \mathrm{m}$ have b... more InGaAsP/InP high pulsed power lasers operating in the range of $1.3 - 1.6\ \mu \mathrm{m}$ have been intensely studied recently, with LIDAR technology being the primary application. We present and analyse a design with a bulk active layer which has a large refractive index step with respect to the optical confinement layer and is located close to the $p$-cladding. It is shown that such lasers can allow a noticeable performance increase over the state of the art. The dependence of the laser performance on the design parameters including the thicknesses of the active layer and the waveguide, the cavity length, and the waveguide asymmetry, is analysed. It is shown that short cavity lengths (∼1 mm or even shorter) can be used in the design considered for achieving high pulsed power. Due to the significant waveguiding properties of the active layer, the use of both symmetric and asymmetric waveguide designs is possible, with only slightly higher output predicted for the asymmetric one. Both designs allow operation with a single, broad transverse mode enabling high brightness.
Semiconductor Lasers and Diode-based Light Sources for Biophotonics, 2018
We have attempted an overview of fast-pulsating lasers (gain-switched, Q-switched and mode-locked... more We have attempted an overview of fast-pulsating lasers (gain-switched, Q-switched and mode-locked) in various biomedical applications. By necessity, the accents in the chapter have been to an extent coloured by our research experience and interests; apologies are extended to those authors whose work may have been omitted. Different properties of a laser system are important for different applications (e.g., high instantaneous and average power for multiphoton spectroscopy vs. spectral tuning range for OCT), but all the designs above benefit from the properties of semiconductor lasers such as chip compactness, ease of pumping, and high gain per unit length. The use of nanostructures, particularly QDs, has been shown to open new exciting opportunities.
Semiconductor Lasers and Laser Dynamics VIII, 2018
Vertical External Cavity Surface Emitting Lasers (VECSELs) have been used for mode-locked operati... more Vertical External Cavity Surface Emitting Lasers (VECSELs) have been used for mode-locked operation by using a Semiconductor Saturable-Absorber Mirror (SESAM), usually in the external cavity [1] but also integrated in the gain-chip [2]. Impressive progress has been achieved since the first demonstration of an SESAM mode-locked VECSEL in terms of pulse duration, average optical power, and peak power. While the shortest pulses have been achieved with optically pumped active layers, electrically pumped structures are promising for a number of applications. Α versatile and accurate, if fairly complex, delay-differential theoretical model for mode-locking in electrically pumping VECSELs based on the physical description of gain and SESAM chips has been presented [3], however only the linear cavity geometry has been studied. A somewhat different approach was taken in [4][5] where an experiment-informed model representing the laser somewhat artificially as a sequence of gain, absorber, and dispersion elements in a unidirectional ring cavity (reminiscent of the classic Haus theory) was developed, and successfully reproduced the measured laser parameters in both pico-and femtosecond regimes. In the current work, we present a somewhat simplified model based on the physical laser design as in [3], which however can accommodate realistic geometry, both linear and folded-cavity. The model is applied to study different regimes of laser operation, including the possibility of colliding pulse mode locking at harmonics of the fundamental roundtrip frequency. As in [3], we base the derivation on the analysis of amplitudes of waves incident onto, and reflected from, elements of the laser cavity, using the amplitude of the field reflected from the “bulk” of the cavity as the dynamic variables for the description of light. Standard rate equations are used for carrier densities. In the case of a linear cavity the model is thus somewhat similar to that used in [3] though somewhat simplified. No matrices of the type used in [3] are needed to recalculate the dynamic variables in our simplified model. The use of phenomenological gain-carrier density dependences and linewidth enhancement factors, while less rigorous than the simplified microscopic model of [3], enables relatively easy inclusion of polarization dependences, allowing double-polarisation frequency comb generation to be simulated. In the case of a folded (Z-type) cavity either the gain chip or the SESAM chip can be positioned “inside” the cavity. The dynamic variables in the case of the gain chip in the middle are the fields reflected from the bulk of the gain chip in the directions of the output mirror and the absorber chip, and from the bulk of the SESAM back to the gain chip . In the case of the gain chip in the middle position, the difference in the dynamics of the saturation of the gain chip changes the pulse parameters and stability limits compared with the linear cavity, but there is no qualitative difference. In the case of the absorber section in the intracavity position, colliding pulse dynamics was simulated with a rational relation between the delay times. Further results will be presented at the conference. References [1] U. Keller, A. C. Tropper, Phys. Reports, 429, 67 (2006) [2] D.J.H.C. Maas et al., Appl Phys B, 88, 493 (2007) [3] J. Mulet and S. Balle, IEEE J. Quantum Electron., 41, 1148 (2005) [4] M. Hoffmann et al., Opt. Express 18, 10143 (2010) [5] O.Sieber et al., Appl.Phys.B., 113, 133-145 (2013)
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