High-dispersive mirrors for femtosecond lasers

Pervak, Vladimir; Teisset, Catherine Y.; Sugita, Atsushi; Naumov, S.; Krausz, Ferenc; Apolonski, Alexander

doi:10.1364/oe.16.010220

Cited by 97 publications

(52 citation statements)

References 21 publications

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“…Proportionality between the absorptance and the GD is very important for application of ultrabroadband chirped mirrors (UBCMs) [7] or highly dispersive mirrors [8] in high power, pulsed laser systems: these mirrors are used for broadband feedback and dispersion compensation, and their reflection GD is typically one or two orders of magnitude higher than that of the low-dispersion QW stacks. However, low reflection loss is crucial in case of dielectric mirrors designed for such lasers: the absorbed power of the laser beam is transformed to heat, which can lead to wavefront distortion or, worse, damage to the coating due to a linear absorption process, which is the dominating damage mechanism for >50 ps pulse durations [9] .…”

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confidence: 99%

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Relationships among group delay, energy storage, and loss in dispersive dielectric mirrors

Antal

Szipöcs

2012

中国光学快报

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We show that absorbed and stored electromagnetic energy are proportional to the reflection group delay in highly reflective dispersive dielectric mirrors over the high-reflectivity band. Our theoretical considerations are verified by numerical simulations performed on different dielectric mirror structures. The revealed proportionality between group delay and absorbed energy sets constraint on the application of ultrabroadband and/or dispersive dielectric mirrors in broadband or widely tunable, high-power laser systems.OCIS codes: 310. 6805, 140.3330, 260.2030. doi: 10.3788/COL201210.053101.In the last two decades, theoretical and experimental investigations on reflection delay time of optical pulses reflected by multilayer dielectric structures have been of scientific interest because frequency-dependent group delay (GD) of the dielectric mirrors can be well suited for intracavity or extracavity dispersion compensation of ultrashort pulse lasers [1] . Aperiodic dielectric mirror structures, which are often referred to as chirped mirrors, are advantageous, not only because they introduce a certain amount of negative dispersion, but also because they exhibit a considerably broader highreflectance band than standard, low-dispersion quarterwave (QW) mirror stacks. Aside from chirped mirrors, there is another group of dispersive mirrors referred to as: Gires-Tournois interferometer-type mirrors [2] . The fact that a relationship exists between the electromagnetic energy stored in the volume of a thin-film structure and its GD is known in the field of telecommunication technology [3] . This relationship is also a starting point in resolving the long-haul scientific problem of superluminal delay times of electromagnetic wave packets during transmission through highly reflective, lossless photonic bandgap structures [4] . In practical laser systems, however, one usually cannot neglect the absorption (or scattering) loss of dielectric multilayer mirrors because laser performance, such as intracavity loss, beam quality, maximum output power, laser damage threshold power, and others, strongly depends on these physical quantities. From this aspect, one can address the question of whether a general relationship exists between the reflection GD and the absorption loss of a dielectric multilayer mirror (throughout the letter, we mean one-photon or linear absorption when we use the word "absorption"). For QW-stack mirrors, GD and absorptance have been shown as proportional to each other at the central wavelength of the QW mirror when the loss is sufficiently low [5] . For a specific multistack multilayer mirror design, Ferencz et al. also found conspicuous, but unexplained, proportionality of these two physical quantities [6] . For a nonspecific, general, highly reflective dielectric mirror structure, however, neither the relationship between GD and the absorptance nor the relationship between GD and the stored energy in the presence of loss has been investigated systematically thus far.In this letter, we first theoretically d...

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“…[7], whereas the HS MCGTI design is the reoptimized version of a structure reported in Ref. [8]. We designed the LS MCGTI to have nearly the same overall optical thickness as the HS MCGTI mirror and a very similar GD versus wavelength function.…”

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Relationships among group delay, energy storage, and loss in dispersive dielectric mirrors

Antal

Szipöcs

2012

中国光学快报

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“…The proposed design is approximately 15 layers and 1.8 µm thickness less than the design in Ref. [7]; however, the GDD resonance and the average reflectivity of the two designs are comparable.…”

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confidence: 73%

“…The design targets are the same as the design in Ref. [7] (e.g., R=100% and GDD=-1 300 fs 2 ). The proposed design consists of a silver layer and 68 dielectric layers, resulting in a total thickness of approximately 8.3 µm.…”

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Dispersive mirrors designed with mixed metal multilayer dielectric stacks

Zhang¹,

Wang²,

Cheng³

2012

中国光学快报

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A different approach to construct dispersive mirrors (DMs) for ultrafast applications is proposed based on the high reflectivity and constant phase property of a novel metal in ultrawide spectral band. A 200-nm bandwidth DM, a high dispersive DM, and a complementary DM are designed with mixed metal multilayer dielectric stacks. The results show that the mixed-metal multilayer dielectric DMs (MMDMs) have much less layers and total thickness compared with an all-dielectric DM under the case of comparable performance. Such an approach will save manufacturing time and remarkably improve the stress of the DM.OCIS codes: 310. 4165, 310.3915, 320.5520. doi: 10.3788/COL201210.013101. Ultrafast lasers that generate high-energy pulses with broad bandwidth have found widespread applications in various fields, such as laser-matter interaction, medical applications, and attosecond pulse generation [1,2] . To generate femtosecond pulses, the material dispersion must be well compensated. Dispersive mirrors (DMs) can provide controllable and high-order dispersion over broadband spectra, making them key elements in ultrashort laser systems [3] . DMs were first proposed by Szipocs et al. in 1994 [4] . Since then, various DMs covering a wavelength range from visible to infrared with a group delay dispersion (GDD) that ranges from zero to values of approximately -2000 fs 2 have been designed, manufactured [5−7] , and utilized in ultrafast systems, including laser oscillators, extra-cavity fiber compressors, and optical parametric amplifiers [8] . Researchers continue the effort to develop novel design and fabrication method of DMs [9−13] . As verified experimentally, in order to provide high reflectivity and the required GDD, the DMs must always have many dielectric layers and very large total thickness, especially for the ultrabroadband and high DMs. Moreover, conventional DMs are usually manufactured by magnetron sputtering and ion-beam sputtering techniques. Such sputtering techniques operate at a slow deposition rate and high energy to improve the accuracy of the manufacture. Thus, the deposition processes are always very time-consuming, and the coatings possess very high stress, distorting the wave front [14] . One solution to these problems is to minimize the coating thickness. In this letter, the feasibility of mixed-metal multilayer dielectric DM (MMDM) is studied. Considering the high broadband reflectivity and the phase property of the metal, a metal layer is inserted between the substrate and some pairs of dielectric layers to constitute a novel DM. The design results show that MMDM can provide characteristics comparable to the all-dielectric DMs, but with much less layer number and thickness. Therefore, deposition time should be reduced, and the stress should be improved significantly.We first focus on the DM with 200-nm bandwidth, which is required for a laser pulse shorter than 10 fs. We consider BK7 glass as a substrate, and tantalum pentoxide (Ta 2 O 5 ) and silicon dioxide (SiO 2 ) as layer materials. The r...

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“…For its efficient operation, such lasers require strong dispersion compensation elements, which are most efficiently realized with chirped mirrors [3]. Most such mirrors are based on dielectric materials due to their high refractive index contrast Because of the large number of mirror layers that can be independently tuned by adjusting their thickness, such an approach-and the structure optimization in particular-is not a trivial task.…”

Section: Introductionmentioning

confidence: 99%

Optimization of broadband semiconductor chirped mirrors with genetic algorithm

et al. 2016

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and high damage threshold. However, the high refractive index contrast results in low number of distributed Bragg reflector (DBR) pairs and, consequently, constant value of high negative GDD can be hard to achieve over a broad band (around 10 nm near the 1-µm wavelength) with such mirrors. On the other hand, semiconductor chirped mirrors have lower refractive index contrast and, thus, require more DBR pairs, which allows to provide better separation of reflection of different wavelengths and makes it easier to tune constant negative GDD over a broader band. In our previous works [4][5][6] we have demonstrated tunable semiconductor double-chirped mirrors with negative dispersion for applications in femtosecond lasers operating near 1 µm. We have fabricated them using arsenide-based molecular beam epitaxy (MBE), and with intentionally introduced layer thickness spatial gradient, we were able to make the mirror properties (reflectivity and dispersion) tunable over an 80-nm range across the mirror surface. We demonstrated tunable mode-locked femtosecond operation of an Yb:KY(WO 4 ) 2 diode-pumped laser oscillator at the 1035-nm wavelength.We obtained negative group-delay dispersion (GDD), necessary for the femtosecond laser operation in the soliton regime, by using a double chirp of the mirror stack that resulted in different wavelengths being reflected at different depths within the semiconductor stack. In our mirror design, we followed classical approach, using an analytical formula [7]. However, to apply this formula we had to make a number of approximations [8], which resulted in a non-optimal mirror design. Hence, we have decided to focus our research on using exact numerical solutions of Maxwell equations and to perform computer optimization in order to achieve a structure with lower mean GDD spanning over a wider bandwidth with reduced oscillations. AbstractGenetic algorithm was applied for optimization of dispersion properties in semiconductor Bragg reflectors for applications in femtosecond lasers. Broadband, large negative group-delay dispersion was achieved in the optimized design: The group-delay dispersion (GDD) as large as −3500 fs 2 was theoretically obtained over a 10-nm bandwidth. The designed structure was manufactured and tested, providing GDD −3320 fs 2 over a 7-nm bandwidth. The mirror performance was verified in semiconductor structures grown with molecular beam epitaxy. The mirror was tested in a passively mode-locked Yb:KYW laser.

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High-dispersive mirrors for femtosecond lasers

Cited by 97 publications

References 21 publications

Relationships among group delay, energy storage, and loss in dispersive dielectric mirrors

Relationships among group delay, energy storage, and loss in dispersive dielectric mirrors

Dispersive mirrors designed with mixed metal multilayer dielectric stacks

Optimization of broadband semiconductor chirped mirrors with genetic algorithm

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