The phrase "after a week when" is correct and usable in written English.
It can be used to refer to a specific time period that follows a week characterized by certain events or conditions.
Example: "After a week when the weather was unusually warm, we finally got some rain."
Alternatives: "following a week in which" or "after a week that".
The descent into bankruptcy came after a week when investors fled MF Global and credit ratings agencies cut their ratings on the firm to junk status.
I opened the store and we had our second largest day ever, after a week when Myrtle Avenue looked like a ghost town.
Wonder performed in London after a week when the US saw five police officers killed in apparent revenge for the deaths of two black men in police shootings.
But, after a week, when their position still hadn't changed, Williams asked to have a conversation with Sandra, "woman to woman".
After a week when simple peanut butter and jelly sandwiches sustained brave rescue workers, pretentious restaurants are not apologizing for their existence.
The farmers had occupied the hall for thirty-nine days, although they had ended their hunger strike after a week, when Simbula's wife, Maria Bonaria, who suffers from a kidney condition, went into shock and was hospitalized.
The first dent to morale came after about a week when the volunteers were first issued ranks in the Rhodesian Army.
Anna* left her own Paris-based study-abroad program after only a week when she experienced a sudden flare-up of her pre-existing OCD.
This has been a week when, after three rounds, Woods has missed, by millimetres, more putts than in the rest of this season put together.
Embryonic fibroblasts should be used within a week when plated after inactivation.
Wales bring the curtain down on their memorable World Cup campaign after a difficult week when they lost by a point to semi-final opponents France and had captain Sam Warburton sent off.
