Six-telescope integrated optics beam combiner fabricated using ultrafast laser inscription for J- and H-band astronomy
Aline N. Dinkelaker, Sebastian Smarzyk, Abani S. Nayak, Simone Piacentini, Giacomo Corrielli, Roberto Osellame, Ettore Pedretti, Martin M. Roth, and Kalaga Madhav
Aline N. Dinkelaker,1,*
Sebastian Smarzyk,1,2
Abani S. Nayak,1,3
Simone Piacentini,4,5
Giacomo Corrielli,5
Roberto Osellame,5
Ettore Pedretti,6
Martin M. Roth,1
and Kalaga Madhav1
1Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
Aline N. Dinkelaker, Sebastian Smarzyk, Abani S. Nayak, Simone Piacentini, Giacomo Corrielli, Roberto Osellame, Ettore Pedretti, Martin M. Roth, and Kalaga Madhav, "Six-telescope integrated optics beam combiner fabricated using ultrafast laser inscription for J- and H-band astronomy," Appl. Opt. 62, 7596-7610 (2023)
We have built and characterized, to our knowledge, the first six-telescope discrete
beam combiner (DBC) for stellar interferometry in the astronomical
J-band. It is the DBC with the largest number of beam combinations and
was manufactured using ultrafast laser inscription in borosilicate
glass, with a throughput of $\approx 56\%$. For calibration of the
visibility-to-pixel matrix, we use a two-input Michelson
interferometer and extract the complex visibility. A visibility
amplitude of 1.05 and relative precision of 2.9% and 3.8% are
extracted for 1328 nm and 1380 nm, respectively.
Broadband (${\leq}{40}\;{\rm nm}$) characterization is affected by
dispersion but shows similar performance.
Abani Shankar Nayak, Thomas Poletti, Tarun Kumar Sharma, Kalaga Madhav, Ettore Pedretti, Lucas Labadie, and Martin M. Roth Opt. Express 28(23) 34346-34361 (2020)
Jacopo Siliprandi, David G. MacLachlan, Calum A. Ross, Tarun K. Sharma, Lucas Labadie, Kalaga Madhav, Abani S. Nayak, Aline N. Dinkelaker, Martin M. Roth, Nicholas J. Scott, Vincent Coudé du Foresto, Robert R. Thomson, and Aurélien Benoit Appl. Opt. 63(1) 159-166 (2024)
Abani Shankar Nayak, Lucas Labadie, Tarun Kumar Sharma, Simone Piacentini, Giacomo Corrielli, Roberto Osellame, Éric Gendron, Jean-Tristan M. Buey, Fanny Chemla, Mathieu Cohen, Nazim A. Bharmal, Lisa F. Bardou, Lazar Staykov, James Osborn, Timothy J. Morris, Ettore Pedretti, Aline N. Dinkelaker, Kalaga V. Madhav, and Martin M. Roth Appl. Opt. 60(19) D129-D142 (2021)
Pierre Haguenauer, Jean-Philippe Berger, Karine Rousselet-Perraut, Pierre Kern, Fabien Malbet, Isabelle Schanen-Duport, and Pierre Benech Appl. Opt. 39(13) 2130-2139 (2000)
Aurélien Benoît, Fraser A. Pike, Tarun K. Sharma, David G. MacLachlan, Aline N. Dinkelaker, Abani S. Nayak, Kalaga Madhav, Martin M. Roth, Lucas Labadie, Ettore Pedretti, Theo A. ten Brummelaar, Nic Scott, Vincent Coudé du Foresto, and Robert R. Thomson J. Opt. Soc. Am. B 38(9) 2455-2464 (2021)
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
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Given is the name of the beam combiner or instruments, the number of inputs for combination (either telescopes or sub-apertures in aperture masking), and the wavelength range ($\lambda$) in terms of astronomical band. The principle of operation is described in terms of beam combination (pairwise or all-in-one) and fringe encoding (temporal, spatial, or matricial); see [33]. Shown is also the status, which indicates whether an integrated optics beam combiner has been tested on-sky (O), the instrument is under commission (UC), or is commissioned (C), and the respective telescope facility. Although the beam combiner presented here has been tested in the laboratory (L) and not yet at a telescope, it is added for comparison. While there are other integrated optics beam combiners with laboratory results, these are not included in this table. The final column includes references.
Table 2.
Side-by-Side Comparison of the Six-Input SPICA-FT Beam Combiner [18] and the Six-Input DBC with Fan-Ina
SPICA-FT
Fan-In DBC
Beam combiner type
ABCD
DBC
Number of inputs
6
6
Number of outputs
60
41
Operating wavelengths
H-band
J-band (/ H-band)
Throughput
56 %
Chip footprint
Fabrication
Lithography
ULI
Instrumental contrast
Crosstalk
0.1 %
N/A
The instrumental contrast for SPICA-FT is given as the average for all baselines and 27 spectral channels between 1.45 and 1.65 µm [18]. The instrumental contrast for the fan-in DBC is the average over all baselines for 51 monochromatic measurements between 1.28 and 1.38 µm, calculated from the V2PM as described in [38]. Crosstalk is not defined for a DBC, as light is expected to spread across all WGs. Note that the footprint of the fan-in DBC is for a chip with 12 beam combiners and could be reduced.
Table 3.
Overview of CN, Relative Precision, and Visibility Amplitudes and Their Sample Standard Deviations for J-band and H-band Measurementsa
Av. Visibility
Av. Precision
Design
Example
(nm)
CN
Type 1 (straight)
Best (J-band)
1294
17
2.8%
Type 2 (fan-in)
Best (J-band)
1328
22
2.9%
Mono (J-band)
1340
38
4.7%
Mono (J-band)
1350
37
4.7%
Mono (J-band)
1380
27
3.8%
Broad (J-band)
1350
32
4.9%
Best (H-band)
1520
34
4.8%
Mono (H-band)
1550
23
6.7%
Broad (H-band)
1550
26
4.8%
For both the extracted mean visibility amplitude and its standard deviation, the average values over all 15 baselines are given. From these average values, the average relative precision is calculated in the last column. Chosen are wavelengths where the relative precision is lowest (“Best”) and some that correspond to the data shown in the figures within this paper. Dataset M1(J) is used for type 2 monochromatic J-band data. Trimmed data containing $\approx 10$ fringes around the mean zero optical path difference are used for the broadband characterization.
Tables (3)
Table 1.
Overview of Integrated Optics Beam Combiners Tested On-Sky or Part of Instrumentsa
Given is the name of the beam combiner or instruments, the number of inputs for combination (either telescopes or sub-apertures in aperture masking), and the wavelength range ($\lambda$) in terms of astronomical band. The principle of operation is described in terms of beam combination (pairwise or all-in-one) and fringe encoding (temporal, spatial, or matricial); see [33]. Shown is also the status, which indicates whether an integrated optics beam combiner has been tested on-sky (O), the instrument is under commission (UC), or is commissioned (C), and the respective telescope facility. Although the beam combiner presented here has been tested in the laboratory (L) and not yet at a telescope, it is added for comparison. While there are other integrated optics beam combiners with laboratory results, these are not included in this table. The final column includes references.
Table 2.
Side-by-Side Comparison of the Six-Input SPICA-FT Beam Combiner [18] and the Six-Input DBC with Fan-Ina
SPICA-FT
Fan-In DBC
Beam combiner type
ABCD
DBC
Number of inputs
6
6
Number of outputs
60
41
Operating wavelengths
H-band
J-band (/ H-band)
Throughput
56 %
Chip footprint
Fabrication
Lithography
ULI
Instrumental contrast
Crosstalk
0.1 %
N/A
The instrumental contrast for SPICA-FT is given as the average for all baselines and 27 spectral channels between 1.45 and 1.65 µm [18]. The instrumental contrast for the fan-in DBC is the average over all baselines for 51 monochromatic measurements between 1.28 and 1.38 µm, calculated from the V2PM as described in [38]. Crosstalk is not defined for a DBC, as light is expected to spread across all WGs. Note that the footprint of the fan-in DBC is for a chip with 12 beam combiners and could be reduced.
Table 3.
Overview of CN, Relative Precision, and Visibility Amplitudes and Their Sample Standard Deviations for J-band and H-band Measurementsa
Av. Visibility
Av. Precision
Design
Example
(nm)
CN
Type 1 (straight)
Best (J-band)
1294
17
2.8%
Type 2 (fan-in)
Best (J-band)
1328
22
2.9%
Mono (J-band)
1340
38
4.7%
Mono (J-band)
1350
37
4.7%
Mono (J-band)
1380
27
3.8%
Broad (J-band)
1350
32
4.9%
Best (H-band)
1520
34
4.8%
Mono (H-band)
1550
23
6.7%
Broad (H-band)
1550
26
4.8%
For both the extracted mean visibility amplitude and its standard deviation, the average values over all 15 baselines are given. From these average values, the average relative precision is calculated in the last column. Chosen are wavelengths where the relative precision is lowest (“Best”) and some that correspond to the data shown in the figures within this paper. Dataset M1(J) is used for type 2 monochromatic J-band data. Trimmed data containing $\approx 10$ fringes around the mean zero optical path difference are used for the broadband characterization.
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