Development of InP Immersion Grating for the near to mid infrared wavelength

Transcription

1 Paper No.54 Development of InP Immersion Grating for the near to mid infrared wavelength Takashi. Sukegawa Y.Okura, T.Nakayasu

2 Outline Introduction Immersion grating by CANON InP immersion grating Summary

3 Introduction Diffractive Optics in CANON Canon Fabrication tool

4 Diffractive optics by CANON DoE for Camera LENS Large Reflection Echelle Grating L360mm x W60mm Large Transmittance Grating Immersion Grating Grism L180mm x W60mm x t1mm L155mm x W42mm ZnS( 10mm)

5 High Precision Cutting Free Form Mechanical Cutting tool High precision by just cutting - Placement Error : < 2nm(RMS) - Surface roughness : < 1nm(RMS) 3D view(afm) 5,000 grooves/mm 200nm/pitch SEM 50,000 grooves/mm 20nm/pitch reserved

6 Immersion Grating by CANON

7 What is immersion grating (IG)? Idea is simple and very old: If diffraction surface is immersed in a medium of refractive index n, wavelength shrinks by 1/n that effectively increases the angular dispersion by n-times. Being able to get either n-times higher spectral resolution or 1/n-th smaller instrument with the same resolution

8 Grating patterning into IR Crystals Anisotropic Etching (chemical) -Only applicable to Silicon. -Apex angle is fixed to 70.52deg (ideal deg) Machining (physical) -Applicable to a variety material Ge, CdTe/CZT, ZnSe/ZnS, KRS5 - Theoretically ideal grating shape can be obtained - But it is very difficult to achieve the required optical quality

9 Development History of immersion grating 2011~ : CdZnTe for space telescope (SPICA) 2014~ : Germanium(Ge) for space and ground telescope Our development is advanced to short wavelength from long wavelength. 2μm 20μm Ge(n=4) CdZnTe(n=2.6) Wavelength (um)

10 Machining Diamond Tool Prism Cutting Direction 2012 SPIE Astronomical Telescopes +Instrumentation Sukegawa et al CANON Inc

11 CdZnTe immersion grating 22mm Mag : x mm Mag : x300 New View 3D Surface roughness 3.2nm RMS 2012 SPIE Astronomical Telescopes +Instrumentation Sukegawa et al Applied Optics 2015 Ikeda et al

12 Ge immersion grating Groove Pitch 56.7um Blaze Angle 75 Apex Angle mm 42mm 34mm 34mm

13 Grooves of Ge immersion grating Mag : x100 Mag : x10,000 Mag : x500 5μm 2016 SPIE Astronomical Telescopes +Instrumentation Sukegawa et al

14 Optical Performances of Ge immersion Grating Items Target Results Surface Flatness (wavefront error) PV < 125nm > 60% Order = 178th PV 54nm RMS 7.3nm 75.3%(TE) 79.7%(TM) L115mm Surface Flatness

15 Largest Ge immersion grating 42mm 155mm Groove Pitch 91.74um Blaze Angle 75 Apex Angle 85

16 Development of InP Immersion Grating The first completed InP immersion grating

17 What is InP? InP is used in high-power and high-frequency electronics because of its superior electron velocity with respect to the more common semiconductors silicon and gallium arsenide. InP is widely used for the optical(lds and LEDs) and the electronic (HBTs and HEMTs) devices as key materials. Nowadays, the applications of InP is extended for various fields such as infrared imaging sensors and high efficiency solar cells.it also has a direct bandgap, making it useful for optoelectronics devices like laser diodes. InP is also used as a substrate for epitaxial indium gallium arsenide based optoelectronic devices. 300mm

18 Design of the first InP immersion grating Prisum Size Groove Area Groove Pitch Blaze Angle Length : 47mm Width : 20mm Height : 16.7mm Ruled : 48mm Width: 19mm 47.3um 72 47m m 86 20mm 72 Apex Angle μm

19 The first InP immersion grating Grooved Area

20 Surface Flatness Groove Direction Ruled Direction +100nm PV PV : 53.5nm RMS : 12.1nm TWIST RMS: 2.5nm 53.5nm 12.1nm (in an area 14.7 mm 18.9 mm) -100nm TWIST 2.5nm Measurement setup 633nm Interferometer (Zygo)

21 SEM Picture of Grooves X200 x1000 X5000

22 Surface roughness of the Groove Counter 45um Blaze 17.8um Placement 2 rd groove(start) 990 th groove(end) Blaze facet ( 100) 8um x 30um Surface roughness(rms) Limitation by physical intervention 1.8nm (13.4nm PV) Counter facet ( 50) Surface roughness (RMS) 30um x 30um 2.2nm (11.4nm PV) 2.7nm (13.5nm PV) Measured by the Zygo New View 3D surface profiler

23 The first completed InP immersion grating Back-reflection coating on the grooved surface Anti-Reflection coating on the entrance/exit surface

24 Measurement Setup of Absolute Diffraction Efficiency Gold mirror (Reference) Projection LENS Diffraction lights Beam size:φ5mmlaser monitor Tunable IR Laser um Cooled 2D InSb Camera Diffraction light Reference light

25 Absolute Diffraction 1.55μm Absolute Diffraction Efficiency (%) 85% 80% 75% 70% 65% Maximum : 80% Maximum : 70% Order = 180th TE 60% 55% TM 50% Wavelength(nm)

26 Summary of optical Performances Items Target Results Surface Flatness (wavefront error) PV < 150nm PV 53.5nm RMS 12.1nm > 60% 80%(TE) 70%(TM) 75%(Average) Ghost - No typical Ghost Evaluation of Diffraction Pattern by 532nm

27 SUMMARY

28 The cover range of wavelength 1.4μm 20μm InP(n=3.1) Ge(n=4) CdZnTe(n=2.6) Wavelength (um) H,K-band, Laser communication at 1.55um

29 Summary Canon succeeded in fabricating the first completed InP immersion echelle grating. In addition to CdZnTe and Ge, Canon would also supply InP immersion grating. Canon is going to continue the development of custom grating which is not only immersion but also conventional. Canon, through its technologies, will continue contributing to the development of the world s scientific technologies and natural science.

30 Conventional echelle grating for IR

31 Thank you for your attention

32 Measurement setup for Diffraction Pattern Diffraction lights Beam size:φ2mm Diffraction Pattern on CCD 543.5n m 2D Projecti on LENS Unit Cooled CCD Camera (4Kx4K) Diffraction Pattern 1D

33 Diffraction pattern evaluation by 543.5nm

34 Freeform Cutting machine 5-AXIS Liner : 3 axis Rotate : 2 axis Process Area 300 x 300 x 200 (mm) Canon Original

35 Largest Ge immersion grating

36 Measurement Setup of Absolute Diffraction Efficiency Gold mirror (Reference) Projecti on LENS Diffraction lights Beam size:φ5mmlaser monitor 4um Tunable IR Laser (Cascade Laser) Cooled 2D InSb Camera Diffraction light Reference light

37 LIMITATION OF SIZE InP (1) 6 inches: I become the prediction dimensions of the ideal form. 1 Length in the case of 3.1 times of the end face : L=130mm(End face 41.9 mm ) 2 Length in the case of 3.8 times of the end face : L=135mm(End face 35.5 mm ) (2) 4 inches: 3 Length in the case of 3.1 times of the end face : L=90mm(End face 29 mm ) 4 Length in the case of 3.8 times of the end face : L=91.2mm(End face 24 mm )

38 Diffraction pattern evaluation by 543.5nm