Pitch Reducing Optical Fiber Arrays (PROFAs) provide low loss, high density coupling for a myriad of applications, including:
Unlike typical fiber arrays, PROFAs provide high density coupling that, for example, minimizes the valuable chip real estate needed for optical input/output (I/O) for fiber-to-chip applications.
PROFAs can provide spot size conversion between small cross-section, chip-based waveguides and standard optical fibers, for example. PROFAs can also maintain, or even increase, mode field sizes, independent of changing channel-to-channel spacing, as might be critical for high power applications.
PROFA1Ds are available as single-channel device or as linear arrays up to six channels. PROFA1Ds are typically used for chip edge coupling to waveguides, for example, with approximately 2 μm diameter mode field sizes.
Two-dimensional (2D) PROFAs are typically used for chip surface coupling to vertical grating couplers with mode field diameters of approximately 6 or 10 μm or to chip-based devices such as VCSELs or photodiodes. Standard PROFA2Ds are available as hexagonal lattice arrays with up to 91 channels.
Other mode field sizes and lattice configurations can be addressed with custom PROFAs.
PROFAs are also used within PIC probing and coupling solutions which you can implement or we can provide.
Form Factor/High Density: Typical lenses cannot be packed closer than 125 microns, compromising the inherent density achievable on-chip. Arrayed PROFAs can feature much tighter spacing.
Polarization: Many waveguides are polarization sensitive and maintaining polarization through a lens to small waveguides is challenging, if not impossible.
Robust connection: PROFAs are intended to be butt coupled to PICs. Eliminating the air gap minimizes the effects of thermal excursions in the package and dust that can make its way into the optical path. The PROFA’s monolithic, all-glass construction enables sealing via adhesives or glass or solder (with metallization) for hermeticity, as needed.
Speak to us about your custom or OEM needs. Custom PROFAs have been supplied to address different channel counts, wavelengths and configurations:
| PARAMETER | UNIT | SINGLE CHANNEL | 6-CHANNEL ARRAY |
|---|---|---|---|
| Central Wavelength 1 | nm | 1550 | |
| Mode Field Size 2 | µm | 1.9 x 2.1 | |
| Bandwidth | nm | >50 | |
| Polarization Extinction ratio, PER 3 | dB | >20 | >16 |
| Insertion Loss 4 | dB | < 1 dB | |
| Optical Return Loss 5 | dB | -22 to -24 | |
| Crosstalk | dB | – | ≤ -40 |
| Number of Channels | 1 | 6 | |
| Channel Spacing | – | 12 | |
| Maximum Channel Position Deviation 6 | µm | – | 0.2 |
| Pigtails 7 | PM, 1 meter long, inside 900 µm furcation tube |
||
| Operating Temperature | C | -40 to +85 | |
| Storage Temperature | C | -70 to +85 | |
| Package Type 8 | M H |
Minimal Holder Compatible 9 |
|
When purchasing a PROFA1D, please use the guide below to determine the best configuration for your application.
PROFA1D-06/12-SM-01-1550-XX-FC/APC-00-MN:
PROFA1D, 6 channels
PROFA1D-04/12-PM-1.5-1550-SO-FC/APC-7.5-MN:
PROFA1D, 4 channels,
PROFA1D-04/12-SM-01-780-XX-00-08-HC:
PROFA1D, 4 channels,
PROFA1D-06/12-SM-01-1550-XX-FC/APC-00-MN:
PROFA1D, 6 channels
Cleaning and Care: PROFAs can be cleaned with alcohol much like a bare fiber tip. Care must be taken to avoid breaking or chipping the tip. Any damage to the tip will likely cause the device to be unusable and unrepairable.
Holder-Compatible Package: The PROFA1D is available with a holder-compatible package design to simplify holding in a standard 6.35 mm (0.25″) diameter fiber chuck holder.
Fiber chuck holding products which hold a 0.25″ (6.35 mm) fiber can be used to hold the PROFA1D with the holder compatible package. This would include some Newport 561 series accessories, like the 561-FC (https://www.newport.com/p/561-FC) or 561-GM (https://www.newport.com/p/561-GM) or similar products from Thorlabs (http://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=1175), for example. There are, of course, other comparable choices as well.
Alignment, Coupling and Packaging: The device is aligned similarly to other micro-optic devices, e.g. similar to working with lensed fibers. Using the PROFA, the most efficient and stable coupling to a waveguide is achieved by butt coupling. Often customers will use index matching liquids or adhesives but this is not required.
PROFA standard products are rigid fiber optic couplers. This product is often used in probing. However, in packaging, when attaching to a die, we typically use a PROFA with a flexible tip. This flexibility enables the PROFA-die interface to be mechanically decoupled from the package. We have developed processes and materials for packaging that may vary, depending on the application needs.
Chiral Photonics will be very supportive in transferring the materials knowledge and process knowledge to our customers. There is a fair amount of customization with regard to coupling that depends on the design (e.g. channel count, mode field size, SM vs. PM, die edge design and quality) and the application needs. Therefore, we strongly suggest that we work with the customer initially to package the device at Chiral Photonics. After we have done that and the customer has received and is satisfied with the packaging, we will transfer the details of materials and process, if desired, so that the customer can take it in-house and just order the couplers and do the packaging themselves. Ideally, after the customer is satisfied with the initial package, we will be happy to host the customer at Chiral Photonics to see how we packaged the device hands-on. Alternately, we can document the packaging process and materials and make that available to the customer.
Rough Alignment: Initial rough rotational alignment of the single channel PROFA1D is easiest done in the far field using a 1550 nm laser and projecting onto an infrared visualizer. One can use this to achieve rough alignment of the device inside a chuck, for example, to the device’s slow/long axis (shorter axis in the far-field). The device is then ready to be aligned finely to, for example, a waveguide.
For the PROFA1D array, rough axial alignment can be done by visually aligning the flats that are parallel to the channel array axis.
Fine Alignment: A five axis stage with at least +/-0.1 micron resolution is typically used for XYZ motion as well as angular alignment. The needed stage resolution will depend on the mode field sizes one is working with and the application. A general rule of thumb is 10% of the mode field diameter, or 0.2 μm for a standard PROFA1D. For an example of one customer’s measured stage resolution requirements of 0.3 microns, please see C. R. Doerr et. al., “Tapered Dual-Core Fiber for Efficient and Robust Coupling to InP Photonic Integrated Circuits,” in Optical Fiber Communication Conference and National Fiber Optic Engineers Conference, OSA Technical Digest (CD) (Optical Society of America, 2009), paper OThN5.