J. Schilling | Martin Luther University Halle-Wittenberg (original) (raw)

Papers by J. Schilling

Applied Physics Letters, 2013

The photoluminescence from plasma etched, wedge shaped Ge-quantum dot arrays is investigated loca... more The photoluminescence from plasma etched, wedge shaped Ge-quantum dot arrays is investigated locally. The wedge geometry allows a convenient measurement of the luminescence intensity within a well defined distance from the etched side facets. A zone of reduced photoluminescence with a thickness of several hundred nanometers is detected adjacent to the etched facets due to the strong non-radiative surface recombination. Covering the surface with thin layers of aluminium oxide passivates part of the surface states leading to a reduction of the luminescence quenching zone.

Conference Digest. 2000 Conference on Lasers and Electro-Optics Europe (Cat. No.00TH8505), 2000

ABSTRACT Summary form only. We have fabricated crystals made of macroporous silicon. A triangular... more ABSTRACT Summary form only. We have fabricated crystals made of macroporous silicon. A triangular lattice of air rods with a lattice constant of 1.5 μm has been etched 100 μm deep into an n-type silicon substrate by electrochemical pore formation in aqueous hydrofluoric acid. A point-defect as well as two linear defects (waveguide structures) are incorporated in the crystal through the appropriate prepatterning of the substrate before etching. A widely tunable continuous wave OPO was used to perform transmission measurements on the structure. The resonance observed in the band gap displayed in the Fourier Transform infrared spectrum is shown. We present our results on structures with various fabrication parameters and geometries. We also show the results of numerical simulations performed by our collaborators and compare them with our experimental measurements

Physical Review B, 2002

Ultrafast tuning of the band edge of a two-dimensional silicon/air photonic crystal is demonstrat... more Ultrafast tuning of the band edge of a two-dimensional silicon/air photonic crystal is demonstrated near a wavelength of 1.9 m. Changes in the silicon refractive index are optically induced by injecting free carriers with 800 nm, 300 fs pulses. The rise time of the shift occurs on the time scale of the pulse width apart from a small component associated with carrier cooling; the recovery time is related to electron-hole recombination. The band edge is observed to shift linearly with pump beam fluence, with a shift in excess of 30 nm for a pump beam fluence of 2 mJ cm Ϫ2. A nonuniform spectral shift is attributed to finite pump beam absorption depth effects.

Metamaterials are artificial materials with unusual properties that do not exist in nature and ba... more Metamaterials are artificial materials with unusual properties that do not exist in nature and basically could consist of subwavelength metallic patterns printed on dielectric substrate. In this paper, we present a theoretical and experimental investigations of metamaterials designed for THz applications. First, fishnet metamaterials which are composed with a thin dielectric material sandwiched between two metallic layers. Two techniques were used in order to fabricate our prototypes: double layer optical lithography and laser micromachining. We performed simulations and experiments using commercial software simulator based on finite element method (HFSS) and terahertz time domain spectroscopy THz-TDS respectively. A good agreement was reported between simulations and experiments while pointed out the dramatic influences of dielectric losses in the effective response.

physica status solidi (a), 2003

A review of the optical properties of 2D and 3D photonic crystals based on macroporous silicon is... more A review of the optical properties of 2D and 3D photonic crystals based on macroporous silicon is given. As macroporous silicon provides structures with aspect ratios exceeding 100, it can be considered as an ideal 2D photonic crystal. Most of the features of the photonic dispersion relation have been experimentally determined and were compared to theoretical calculations. This includes transmission and reflection of finite and bulk photonic crystals and their variation with the pore radius to determine the gap-map. All measurements have been carried out for both polarizations independently since they decouple in 2D photonic crystals. Moreover, by inhibiting the growth of selected pores, point and line defects can be realized and the corresponding high Q microcavity resonances as well as waveguiding properties were studied via transmission. The tunability of the bandgap was demonstrated by changing the refractive index by liquid crystals as well as optically-injected free carriers. Finally different realizations of 3D photonic crystals using macroporous silicon are discussed. In all cases an excellent agreement between experimental results and theory has been observed.

physica status solidi (a), 2000

È ller 1) (a), A. Birner (a), J. Schilling (a), U. Go È sele (a), Ch. Kettner (b), and P. Ha È ng... more È ller 1) (a), A. Birner (a), J. Schilling (a), U. Go È sele (a), Ch. Kettner (b), and P. Ha È nggi (b)

Microsystem Technologies, 2002

Structures with high aspect ratios have been prepared by exploiting the high built-in anisotropy ... more Structures with high aspect ratios have been prepared by exploiting the high built-in anisotropy of some porous materials. For the structuring of these materials with nearly arbitrary shapes only standard lithography and isotropic etching is needed. We demonstrate the power of this technique for macroporous silicon and porous anodic alumina. Structures with sub-micrometer precision and aspect ratios above 100 are shown.

MRS Bulletin, 2001

In the last few years, photonic crystals have gained considerable interest due to their ability t... more In the last few years, photonic crystals have gained considerable interest due to their ability to “mold the flow of light.” Photonic crystals are physically based on Bragg reflections of electromagnetic waves. In simple terms, a one-dimensional (1D) photonic crystal is a periodic stack of thin dielectric films with two different refractive indices, n1 and n2. The two important geometrical parameters determining the wavelength of the photonic bandgap are the lattice constant, a = d1(n1) + d2(n2), and the ratio of d1 to a (where d1 is the thickness of the layer with refractive index n1, and d2 is the thickness of layer n2). For a simple quarter-wavelength stack, the center wavelength λ of the 1D photonic crystal would be simply λ = 2n1d1 + 2n2d2. In the case of 2D photonic crystals, the concept is extended to either airholes in a dielectric medium or dielectric rods in air. Therefore, ordered porous dielectric materials like porous silicon or porous alumina are intrinsically 2D photo...

Journal of Optics A: Pure and Applied Optics, 2001

A review of the optical properties of two-dimensional and three-dimensional photonic crystals bas... more A review of the optical properties of two-dimensional and three-dimensional photonic crystals based on macroporous silicon is given. As macroporous silicon provides structures with aspect ratios exceeding 100, it can be considered to be an ideal two-dimensional photonic crystal. Most of the features of the photonic dispersion relation have been experimentally determined and were compared to theoretical calculations. This includes transmission and reflection of finite and bulk photonic crystals and their variation with the pore radius to determine the gap map. All measurements have been carried out for both polarizations separately since they decouple in two-dimensional photonic crystals. Moreover, by inhibiting the growth of selected pores, point and line defects were realized and the corresponding high-Q microcavity resonances as well as waveguiding properties were studied via transmission. The tunability of the bandgap was demonstrated by changing the refractive index inside the pores caused by an infiltrated liquid crystal undergoing a temperature-induced phase transition. Finally different realizations of three-dimensional photonic crystals using macroporous silicon are discussed. In all cases an excellent agreement between experimental results and theory is observed.

Journal of Applied Physics, 2003

A perfect two-dimensional porous alumina photonic crystal with 500 nm interpore distance was fabr... more A perfect two-dimensional porous alumina photonic crystal with 500 nm interpore distance was fabricated on an area of 4 cm 2 via imprint methods and subsequent electrochemical anodization. By comparing measured reflectivity with theory, the refractive indices in the oxide layers were determined. The results indicate that the porous alumina structure is composed of a duplex oxide layer: an inner oxide layer consisting of pure alumina oxide of 50 nm in thickness, and an outer oxide layer of a nonuniform refractive index. We suggest that the nonuniform refractive index of the outer oxide arises from an inhomogeneous distribution of anion species concentrated in the intermediate part of the outer oxide.

Crystal Growth & Design, 2014

ABSTRACT We report on the synthesis of a novel optoelectronic material, Sn-rich Ge1–xSnx nanocrys... more ABSTRACT We report on the synthesis of a novel optoelectronic material, Sn-rich Ge1–xSnx nanocrystals in a Ge matrix. The nanocrystals have been formed after annealing of a metastable Ge-rich Ge1–ySny film, which was embedded in the Ge matrix. Electron microscopy investigations have revealed that these nanocrystals possess two lattice types: (i) a diamondlike cubic structure with a high Sn fraction (x > 0.5) and (ii) an ordered zincblende structure (x = 0.5).

Applied Physics Letters, 2009

$Research paper thumbnail of Diffraction properties of two-dimensional photonic crystals$

Applied Physics Letters, 2003

We show that the envelope of the diffraction efficiency of a two-dimensional photonic crystal can... more We show that the envelope of the diffraction efficiency of a two-dimensional photonic crystal can exhibit spectral regions of very small diffraction efficiency (Ͻ5ϫ10 Ϫ3), while in other regions, the diffraction efficiency is near unity. The experimental results on higher bands of hexagonal, silicon-based photonic crystals agree well with corresponding numerical calculations and highlight the prominent role of the surface termination, an aspect which cannot be described by the photonic band structure alone. We speculate about possible applications of such additional spectral filters in Raman and photoluminescence spectroscopy.

Applied Physics Letters, 2005

Three-dimensional photonic crystals based on macroporous silicon are fabricated by photoelectroch... more Three-dimensional photonic crystals based on macroporous silicon are fabricated by photoelectrochemical etching and subsequent focused-ion-beam drilling. Reflection measurements show a high reflection in the range of the stopgap and indicate the spectral position of the complete photonic band gap. The onset of diffraction which might influence the measurement is discussed.

Applied Physics Letters, 2004

Macroporous silicon membranes are fabricated whose pores are terminated with 60 nm thin silicon d... more Macroporous silicon membranes are fabricated whose pores are terminated with 60 nm thin silicon dioxide shells. The transmission of electrons with energies of 5 kV-25 kV through these membranes was investigated reaching a maximum of 22% for 25 kV. Furthermore, the transmission of electromagnetic radiation ranging from the far-infrared to the x-ray region was determined. The results suggest the application of the membrane as window material for electron optics and energy dispersive x-ray detectors.

Si-based 2D macroporous photonic crystals (PCs) have become of increasing interest, because of th... more Si-based 2D macroporous photonic crystals (PCs) have become of increasing interest, because of their extraordinary optical properties in the near IR. They are fabricated by electro-chemical pore etching of prestructured Si-wafers with pore diameters in the range of 1.0 mum having a pore depth of about 100 mum. If the radius of the air pores is varied by the growth

The optical properties of photonic crystal and photonic bandgap (PBG) structures have been extens... more The optical properties of photonic crystal and photonic bandgap (PBG) structures have been extensively studied over the past 10 years. Most of the attention has been devoted to calculations and.