Three-dimensional photonic crystals created by single-step multi-directional plasma etching Katsuyoshi Suzuki,1,2 Keisuke Kitano,1,2 Kenji Ishizaki,1,* and Susumu Noda1 1
Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510, Japan 2 These authors contributed equally to this work * [email protected]
Abstract: We fabricate 3D photonic nanostructures by simultaneous multidirectional plasma etching. This simple and flexible method is enabled by controlling the ion-sheath in reactive-ion-etching equipment. We realize 3D photonic crystals on single-crystalline silicon wafers and show high reflectance (>95%) and low transmittance (~80%) was obtained in the wavelength range around 1.0 μm for ax = 450 nm, 0.95 μm for ax = 405 nm, 0.75 μm for ax = 360 nm, and 0.60 μm for ax = 315
#212173 - $15.00 USD (C) 2014 OSA
Received 15 May 2014; revised 20 Jun 2014; accepted 25 Jun 2014; published 3 Jul 2014 14 July 2014 | Vol. 22, No. 14 | DOI:10.1364/OE.22.017099 | OPTICS EXPRESS 17104
nm. Although relatively high reflection (40~50%) was seen in the wavelength around 1.1 μm for ax = 360 nm and 0.95 μm for ax = 315 nm, we assume that they originated from FabryPerot interference. The obtained high-reflectance exceeding ~80% suggests the formation of a photonic bandgap even in such a short wavelength range of 0.6~1.1 μm. Note that the reflectance remained high (>~80%) despite the inherent material absorption of Si due to the band-to-band transition in the wavelength below 1.1 μm. The influence of such an absorption nature on the optical characteristics of the Si-based 3D photonic crystals will be described elsewhere. (a)
530 nm
1 mm
Reflectance
(b)
Transmittance
570 nm
610 nm
1 mm
650 nm
1 mm
1 mm
1.0 0.8 0.6 0.4 0.2 100
10-1 1.2 1.4 1.6 1.8 Wavelength (mm)
1.2 1.4 1.6 1.8 Wavelength (mm)
1.2 1.4 1.6 1.8 Wavelength (mm)
1.2 1.4 1.6 1.8 Wavelength (mm)
Fig. 5. Demonstration of 3D photonic crystals in optical communication wavelengths range. (a) Top-view SEM images for lattice intervals ranging from 530 to 650 nm, (b) measured transmittance and reflectance of structures shown in (a).
(a)
Reflectance
(b)
315 nm
360 nm
1 mm 1.0 0.8 0.6 0.4 0.2 0 0.6 0.8 1.0 1.2 Wavelength (µm)
405 nm
1 mm
0.6 0.8 1.0 1.2 Wavelength (µm)
450 nm
1 mm
0.6 0.8 1.0 1.2 Wavelength (µm)
1 mm
0.6 0.8 1.0 1.2 Wavelength (µm)
Fig. 6. Demonstration of 3D photonic crystals in wavelengths below 1.1 μm. (a) Top-view SEM images for lattice intervals ranging from 315 to 450 nm, (b) measured reflectance of structures shown in (a).
#212173 - $15.00 USD (C) 2014 OSA
Received 15 May 2014; revised 20 Jun 2014; accepted 25 Jun 2014; published 3 Jul 2014 14 July 2014 | Vol. 22, No. 14 | DOI:10.1364/OE.22.017099 | OPTICS EXPRESS 17105
5. Conclusion We have developed and demonstrated a technique for creating 3D photonic nanostructures by simultaneous multi-directional etching. We showed that this method can be used to fabricate 3D photonic-crystal structures on single-crystalline silicon wafers using a single etching step. The fabricated structures exhibited optical properties consistent with the formation of a photonic bandgap in optical communication wavelengths range, implying that the 3D photonic structures were successfully formed as expected. We also demonstrated that the lattice intervals of 3D structures can be varied by simply changing the mask pattern, demonstrating the bandgap effect in wavelengths ranging from 0.6 to 1.1 μm, which requires finer structures. We expect to apply our method to thicker 3D photonic structures by extending the etching time while tuning the etching conditions and the ion-sheath control plate. The formation of various types of 3D structures in a variety of materials would be realized by further developing the design of the ion-sheath control plate, depending on the etching materials and mask patterns. Because our method enables even the batched processing of 3D structures with complex designs, it will promote further progress in research on 3D photonic nanostructures. Acknowledgments This work was supported in part by the Global Center of Excellence Program for Education and Research on Photonic and Electronics Science and Engineering of Kyoto University, Japan, and by a Grant-in-Aid from the Japan Science Promotion Society.
#212173 - $15.00 USD (C) 2014 OSA
Received 15 May 2014; revised 20 Jun 2014; accepted 25 Jun 2014; published 3 Jul 2014 14 July 2014 | Vol. 22, No. 14 | DOI:10.1364/OE.22.017099 | OPTICS EXPRESS 17106
Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510, Japan 2 These authors contributed equally to this work * [email protected]
Abstract: We fabricate 3D photonic nanostructures by simultaneous multidirectional plasma etching. This simple and flexible method is enabled by controlling the ion-sheath in reactive-ion-etching equipment. We realize 3D photonic crystals on single-crystalline silicon wafers and show high reflectance (>95%) and low transmittance (~80%) was obtained in the wavelength range around 1.0 μm for ax = 450 nm, 0.95 μm for ax = 405 nm, 0.75 μm for ax = 360 nm, and 0.60 μm for ax = 315
#212173 - $15.00 USD (C) 2014 OSA
Received 15 May 2014; revised 20 Jun 2014; accepted 25 Jun 2014; published 3 Jul 2014 14 July 2014 | Vol. 22, No. 14 | DOI:10.1364/OE.22.017099 | OPTICS EXPRESS 17104
nm. Although relatively high reflection (40~50%) was seen in the wavelength around 1.1 μm for ax = 360 nm and 0.95 μm for ax = 315 nm, we assume that they originated from FabryPerot interference. The obtained high-reflectance exceeding ~80% suggests the formation of a photonic bandgap even in such a short wavelength range of 0.6~1.1 μm. Note that the reflectance remained high (>~80%) despite the inherent material absorption of Si due to the band-to-band transition in the wavelength below 1.1 μm. The influence of such an absorption nature on the optical characteristics of the Si-based 3D photonic crystals will be described elsewhere. (a)
530 nm
1 mm
Reflectance
(b)
Transmittance
570 nm
610 nm
1 mm
650 nm
1 mm
1 mm
1.0 0.8 0.6 0.4 0.2 100
10-1 1.2 1.4 1.6 1.8 Wavelength (mm)
1.2 1.4 1.6 1.8 Wavelength (mm)
1.2 1.4 1.6 1.8 Wavelength (mm)
1.2 1.4 1.6 1.8 Wavelength (mm)
Fig. 5. Demonstration of 3D photonic crystals in optical communication wavelengths range. (a) Top-view SEM images for lattice intervals ranging from 530 to 650 nm, (b) measured transmittance and reflectance of structures shown in (a).
(a)
Reflectance
(b)
315 nm
360 nm
1 mm 1.0 0.8 0.6 0.4 0.2 0 0.6 0.8 1.0 1.2 Wavelength (µm)
405 nm
1 mm
0.6 0.8 1.0 1.2 Wavelength (µm)
450 nm
1 mm
0.6 0.8 1.0 1.2 Wavelength (µm)
1 mm
0.6 0.8 1.0 1.2 Wavelength (µm)
Fig. 6. Demonstration of 3D photonic crystals in wavelengths below 1.1 μm. (a) Top-view SEM images for lattice intervals ranging from 315 to 450 nm, (b) measured reflectance of structures shown in (a).
#212173 - $15.00 USD (C) 2014 OSA
Received 15 May 2014; revised 20 Jun 2014; accepted 25 Jun 2014; published 3 Jul 2014 14 July 2014 | Vol. 22, No. 14 | DOI:10.1364/OE.22.017099 | OPTICS EXPRESS 17105
5. Conclusion We have developed and demonstrated a technique for creating 3D photonic nanostructures by simultaneous multi-directional etching. We showed that this method can be used to fabricate 3D photonic-crystal structures on single-crystalline silicon wafers using a single etching step. The fabricated structures exhibited optical properties consistent with the formation of a photonic bandgap in optical communication wavelengths range, implying that the 3D photonic structures were successfully formed as expected. We also demonstrated that the lattice intervals of 3D structures can be varied by simply changing the mask pattern, demonstrating the bandgap effect in wavelengths ranging from 0.6 to 1.1 μm, which requires finer structures. We expect to apply our method to thicker 3D photonic structures by extending the etching time while tuning the etching conditions and the ion-sheath control plate. The formation of various types of 3D structures in a variety of materials would be realized by further developing the design of the ion-sheath control plate, depending on the etching materials and mask patterns. Because our method enables even the batched processing of 3D structures with complex designs, it will promote further progress in research on 3D photonic nanostructures. Acknowledgments This work was supported in part by the Global Center of Excellence Program for Education and Research on Photonic and Electronics Science and Engineering of Kyoto University, Japan, and by a Grant-in-Aid from the Japan Science Promotion Society.
#212173 - $15.00 USD (C) 2014 OSA
Received 15 May 2014; revised 20 Jun 2014; accepted 25 Jun 2014; published 3 Jul 2014 14 July 2014 | Vol. 22, No. 14 | DOI:10.1364/OE.22.017099 | OPTICS EXPRESS 17106
